Copper silicides are widely used in microelectronics. Even though the Cu-Si phase diagram is considered well established [1], there are uncertainties concerning the crystal structure of Cu3+xSi. We investigated the crystal structure of Cu3+xSi samples with nominal composition 74%, 76%, and 78% copper. In addition to DSC measurements, we performed temperature-dependent powder XRD and in-situ high-temperature single crystal XRD between 30 °C and 750 °C. Combining these techniques allowed us to identify six phases, instead of the three present in the phase diagram. In order of increasing temperature: η’’’, η’’, η’, η3, η2, and η1. Five out of the six phases were completely indexed by XRD. Except for η1, all the five structures present incommensurately modulation character. η3 had the main reflection indexed, but no modulation vector could be determined. η’’’ and η’’ were solved by single crystal XRD using a supercell approximation in a (3+2)D superspace. Our study shows that the phase diagram might be more complex than that reported in the literature.
In this work, a series of experimental commercial polymer material Stahl1018. Using the techniques of scanning electron microscopy and X-ray microanalysis was performed to study the microstructure of the material and determined the chemical composition of the areas studied, which allowed a tentative identification of the content of metallic elements in the composite. Further experiments made it possible to define the hardness and micro-hardness. It examined the ability of a material to adhere to the metal surface (adhesion) and impact tests were conducted. Research results confirmed the possibility of using the composite as a binder for the repair of mechanical parts and casting. The results are presented in the form of photographs and illustrations. Research results confirmed the possibility of using the composite as a binder for the repair of mechanical parts and casting. On the basis of strength tests determined yield strength of the material. Found maximum stability of the composite at a temperature of 20 0C.
In this work, microstructural changes in as-cast hypoeutectic Zn3Al, eutectic Zn5Al and hypereutectic Zn10Al alloys after heat treatment were analysed. In order to achieve a fine grain microstructure of samples an alloy with corresponding chemical composition was cast into a copper mould and subsequently water cooled down to room temperature. Samples were analysed both in as-cast state as well as after heat treatment at 350°C at different times. Characterization of microstructure was carried out by scanning electron microscopy (SEM) and X-ray diffraction XRD. The analysed alloys consisted of three principal phases. Namely, zinc rich η- phase, aluminium rich α phase and high temperature ZnAl β phase. In case of Zn3Al and Zn10Al typical dendritic-eutectic microstructure was observed. According to Zn-Al equilibrium phase diagram an as-cast microstructure of Zn3Al consisted of η zinc dendrites and eutectic mixture of η zinc and α aluminium phase. As-cast microstructure of Zn10Al consisted of former β phase dendrites decomposed into eutectoid mixture of η and α phase and eutectic mixture of η zinc and α aluminium phase. For the Zn5Al alloy, a fully lamellar eutectic mixture of η zinc and α aluminium phase was observed. It was found out that as-cast microstructure of alloys was significantly affected by heat treatment. More detailed influence of heat treatment on microstructural parameters is discussed based on results from Rietveld analysis of XRD data. Measurement of microhardness of non-heat treated and heat treated samples have shown no major change in mechanical properties.
Twin-roll casting (TRC) is a modern method of preparation of aluminum alloys. The distinctive feature of TRC is the combination of rapid metal solidification and subsequent plastic reduction in a single combined processing step. As a result of intensive heat extraction to the coolant via caster rolls, the melt solidifies and undergoes plastic reduction similar to the rolling process. However, some specific microstructural features of twin-roll cast strips, which restrict applications of this technology, are known. These are localised centreline segregation, surface and near-surface microsegregation and microstructural inhomogeneity. These features lead to the deterioration of mechanical properties of the strips, in particular strength, formability and corrosion resistance and can only be eliminated during a complex thermomechanical treatment. In the present contribution segregations in TRC Al-Mg-Sc-Zr alloy were studied by means of light optical microscopy, electron microscopy and 3D X-ray computer tomography. The spatial distribution was succesfully detected and morfology was described.
One of the most crucial parameters having deciding influence on the quality of multilayer ceramic forms used in precision casting process of aircraft vanes, is their thickness. Traditional measuring methods ensure a possibility of quantitative determining the factor only after inundating the form with liquid metal and breaking it. This article shows the results of the research which aim was to implement the non-destructive method using 3D scanning in order to determine thickness of forms. Three different kinds of ceramic materials and binders were selected and were put on wax model kits. Finally, 7-layers forms were made. Model sets and every of applied layers were scanned with 3D scanner. The results of scanning are generated as stl. files, which means that they describe geometry of the surface. After applying two scans on each other and processing them with the use of software dedicated for scanner, the empty space visible between measured surfaces determine the thickness of each layer and consequently the whole covering. The solution is very profitable as it allows to detect faulty forms and exclude them from subsequent stages of production. It allows to reduce the unnecessary spending which are really enormous in the case of such product. ACKNOWLEDGEMENTS: The work done in the framework of a research project No. PBS3/A5/54/2016 funded by the National Centre for Research and Development.
The rubber stamping technology is not widely applied in industrial practice. This solution has one big advantage concerning tools because it is necessary to make only one forming die, the second is replaced by a rubber stamp. In the result it is possible to prepare tools with significantly reduced cost. The proposed solution is applied in short series of sheet metal parts especially with different shapes of ribs and stiffeners. The example of this technology implementation is fire barrier forming for different types of helicopters according to aviation regulations. In this paper conditions of stiffener ribs forming from titanium alloy CP2 sheets by means of rubber stamping are presented. The influence of die geometry on rubber stamping process is shown basing on numerical simulations results. During calculations the distributions of effective stress, strain and load parameters are given. For experimental verification of the obtained results the models tools are made using 3D printer. The experiment in a laboratory condition was realized using hydraulic press with load distribution recording. Final results of calculations and experiment show the influence of stiffener ribs designing on its final shapes possible to obtain applying rubber stamping technology.
The article presents tests results of the influence of extrusion process on the microstructure and mechanical properties of magnesium alloy with lithium and with symbols LX41 and LX82. Achieved microstructures of magnesium alloys after extrusion were compared with microstructure after casting and homogenisation. Presented results show the mechanical properties marked in static extrusion test in room temperature. It was stated that alloy LX41 is characterised with better plasticity than the alloy LX82.
The effect of welding parameters and groove geometry on the mechanical properties of Tungsten Inert Gas (TIG) welded joints have been analysed in the presented study. Four different groove angles have been chosen to ascertain the tendency of microstructure formation and quality of the weld. Mechanical properties were assessed in the terms of hardness and tensile properties. Microanalysis of test samples produced was done in fusion, partially melted, and heat affected zone; all the images have showed good penetration and clear transition from one to other zone. The transverse tensile tests were accomplished on the welded joints to evaluate influence of welding parameters and groove geometry to the joint tensile strength and its behaviour during exploitation. It was found that the tensile strength of the welds is closely related to the welding parameters: 180A welding current ensured highest tensile strength of test samples, the same as proper selection of groove angle (90°) provides good fusion and high quality of major welds. The results have revealed that the weld penetration depends on welding current. The experimental study showed that the reduction of strength and hardness was caused by the structural instability due to coarsening or over-ageing of the precipitates in HAZ. The region of HAZ close to the weld bead, known as PMZ is harder than the rest of the HAZ, but still softer than the base metal due to the fact that welded joint is under the influence of relatively high temperature and the effect of rapid cooling rate.
HCM in Miasteczko Śląskie is the only zinc smelter in Europe which use Imperial Smelting Process technology. Paper shows ISF charging model which allows to calculate on-line current state of the furnace batch parameters. The main purpose of the model is predicting of raw Zn, Pb and slag production in the next charging step, which can change depending on thermal demands or new chemical composition of the batch. The paper reflects implementation progress of the project financed by European Funds, Operational Programme Smart Growth 2014-2020.
The paper investigates the influence of the layer thickness and the laser spot diameter in the process of selective laser melting, as well as subsequent heat treatment on the structural-phase composition and mechanical properties of the manufactured parts. The possibility of manufacturing parts with a tailored structure from an Inconel 718 superalloy using selective laser melting is demonstrated by varying the technological parameters of the process. In this case, the elements of a part with different grain size and orientation are formed.
The paper presents the results of research on the production of a sintered Cu-SiO2 composites fabricated by powder metallurgy. The starting materials for obtaining the composites were commercial powders: Cu with an average particle size of 63 μm and SiO2 with an average particle size of 45 μm. SiO2 particles were introduced into a copper matrix in the amount of 2.5%, 5%, 7.5% and 10% by weight. Finished powders mixtures were subjected to single pressing with a hydraulic press at a compaction pressure of 620 MPa and then subjected to sintering process at 900 °C in an atmosphere of dissociated ammonia. The sintering time was 60 minutes. The obtained sinters were subjected to the compaction process at a pressure of 620 MPa and then again sintered at 900 °C for 60 minutes. The sintered compacts were subjected to the following tests: hardness, measurement of density, electrical conductivity and abrasion resistance. Observations of the microstructure on metallographic specimens made from the sintered samples were also performed using a scanning electron microscope (SEM). The highest density was obtained for a composite containing 2.5% SiO2 which was 7.94 g/cm3. The highest hardness was obtained for a composite containing 10% SiO2 which amounted to 56.8 HB. For the composite containing 2.5% SiO2 the highest electrical conductivity was obtained which was 47.1 MS/m. The highest abrasive wear resistance was obtained for a composite containing 10% SiO2. Both density and electrical conductivity decreased along with the increase of SiO2 content in composites.
The AZ31/6060 bimetallic material was fabricated through compound casting, which involved pouring AZ31 magnesium alloy heated up to 660 ºC onto a 6060 aluminium alloy insert placed in a steel mould, both preheated to 300 ºC. The microstructural analysis was performed with an optical microscope (OM) and a scanning electron microscope coupled to an energy-dispersive X-ray spectrometer (SEM–EDS). Three characteristic areas could be distinguished in the 400-500 µm thick continuous bonding zone, which formed between the alloys. The EDS quantitative analysis revealed that the area close to the AZ31 was a eutectic (an Mg17Al12 phase and a solid solution of Al in Mg); then, there were dendrites of an Mg17Al12 phase; and finally, in the area adjacent to the 6060 alloy, an Al3Mg2 phase was detected. Fine particles of an Mg2Si phase and phases rich in Al, Mn and Fe were distributed over the entire bonding zone. Small porosity was observed only locally.
Copper processing in slurry furnace (Outokumpu technology) is based on converting copper matte to a blister and slag that contains up to 16% copper oxides. The obtained slag is tapped into the electric arc furnace where the liquid slag (slurry) is extracted by treatment reducers and technological modifiers. In such a refining process, the copper content in the tapping slag is within the range of 0.4-0.8%. However, (the previous analysis indicate, that) further decrease of copper content may be obtained through comprehensive technological activities. Typically, in industrial condition the refining slag in the arc furnace may stay both in static condition and in strong step of stirring e.g. in under electrode zone. The paper discusses the influence of selected technological additives on the reduction of copper oxides in slurry slag as well as coagulation and sedimentation of products in particular conditions. The tests were carried out under static and dynamic conditions of mixing molten slag at 1300oC. Differences in the copper forms (products of reduction reactions) in the post-deposition slag demonstrated the occurrence of coagulation phenomenon.
A new method is proposed to estimation of hydrogen pressure in equilibrium with hydride phase in a hydrogen storage material. It is applicable both for hydrogen absorption and desorption in cases where the hydride phase is formed by nucleation and growth mechanism. The proposed method saves considerably the experimental time replacing the conventional time consuming measurement of pressure-composition isotherms, the so called PCT curves. The proposed evaluation procedure is illustrated using hydrogen chemi-sorption at temperatures 623 K, 573 K and 523 K in chosen hydrogen storage alloys Mg-Si-C, Mg-Li-C and Mg-Na-C.
The paper presents, the impact of process variables on connection parameters during micro-welding of H800 superalloy. The research discusses the apparatus and features, including the advantages of the welding procedure. The process variables determining the influence of pulse micro-welding method on the metallographic structure of welds of thin superalloys were given. The process uses a thin sheet of H800 superalloy welded on a C22 alloy substrate. During the experiment, welded joints of tested super alloys were obtained and the characteristics of their microstructure were examined. Welding of thin sheet was made by means of resistive pulse welding using the SST WS 7000s device. The focus was on the leading tested parameters, such as microhardness and observation of the weld microstructure.
Microhardness measurements in joints using the Matsuzawa Vickers MX 100 with applied load of 100G (0.98 N). The welds were examined using optical and scanning microscopy. EDS analysis of the distribution of key elements in the area of the connection and the heat affected zone was performed.
Three different orientations (ND, 45, RD) of high textured AZ31 sheet have been deformed in compression and tension. The acoustic emission was measured during the deformation and the deformed microstructure was studied by the electron backscatter diffraction. The results shows different evolution of twinning during the deformation.
Sintered permanent magnets based on the Nd2Fe14B intermetallic compound are widely used in industry as a rule in a temperature range of from -60 to 150C. However, in recent years, there appears a need to use such magnets at cryogenic temperatures and mainly at liquid nitrogen temperature (77 K). The natural increase in Br of Nd-Fe-B magnets with falling temperatures is well known phenomenon but is limited to temperatures above 135 K due to the spin-reorientation in Nd2Fe14B-based alloys. At this temperature, the easy-axis magnetic anisotropy changes to easy-axes cone anisotropy. The Pr2Fe14B compound exhibits no spin-reorientation transition up to cryogenic temperatures. Therefore, permanent magnets based on Pr2Fe14B compound are of interest for investigators owing to the capability of these magnets to remain high hysteretic parameters at low and cryogenic temperatures. In this case, the natural increase in the hysteretic parameters with decreasing temperature can be adequately used. The Pr2Fe14B-based magnets (Pr-Fe-Ti-Al-Cu-B) were prepared by traditional powder metallurgy technology, and 3 wt % HoH2 was added to the main powder at the fine-milling stage. The structure of the magnets was studied in detail by scanning electron microscopy (SEM/EDX) and the formation of pronounced so-called “core-shell” structure was demonstrated. The effect of HoH2 hydride addition on the hysteresis loop parameters of sintered Pr-Fe-Ti-Al-Cu-B magnets was studied and the marked improvement of hysteretic parameters was found. Domain structure of the magnets was studied perpendicular and parallel to the magnet texture using magnetic force microscopy. The data obtained indicate the well-formed magnetic texture. The average domain width is 1.2-1.8 m.
Grade 316L is the low carbon austenitic stainless steels with molybdenum content and is immune from sensitisation (grain boundary carbide precipitation). Thus it is extensively used in heavy gauge welded components. The austenitic structure also gives excellent toughness, even down to cryogenic temperatures. The molybdenum gives 316L good overall corrosion resistant properties, particularly higher resistance to pitting and crevice corrosion in chloride environments. Compared to chromium-nickel austenitic stainless steels, 316L stainless steel offers higher creep, stress to rupture and tensile strength at elevated temperatures. These properties are specified for flat rolled product (plate, sheet, pipe, bar and coil) in ASTM A240/A240M.
Thermal treatment of SUS 316L alloys allows significantly influence microstructure and mechanical properties. The aim of this work was the study of microstructure of SUS 316L before and after thermal treatment. The heat regimes were performed at these conditions: 1050, 1100 and 1150 °C for 20, 45 and 70 minutes followed by slow cooling in vacuum. Microstructures features were studied by means of optical and scanning electron microscopies, EDX microanalysis and microhardness measurement. Higher aging temperatures and annealing time led to decreasing microhardness and microstructure changes (grain growth).
Powder bed techniques of additive manufacture, where the product being built is surrounded by a loose powder, yield low-quality surfaces. The powder particles that are in a close contact with the product adhere to its surface, either by thermal diffusion effects or by partial melting by contour scan tracks. The surface of additively manufactured metals has been shown to negatively affect mechanical properties, with the most negative impact on fatigue. Besides, these particles can loosen and cause problems during part operation. With respect to the above-mentioned problems, different ways of surface finish have been applied. In this study, we tested the samples of the Ti6Al4V alloy prepared by selective laser melting with three different surface finishes (as-built, machined and machined + tumble polished), and subjected them to high-cycle fatigue tests. Although many authors have reported on the positive effect of a surface finish on fatigue, in this study, we show that it might not always be true.
Current tin recovery processes from steel sheets of scrapped cans are mainly based
on hydrometallurgical methods using water solutions of acids and bases. Due to the universally binding tendency forcing activities aimed at improving the efficiency of production processes, also in the case of hydrometallurgical methods of metal recovery, it is necessary to look for new economic technological solutions. One of many such activities may be the initial impact machining of sheets of scrapped cans subjected to tin recovery, the result of which may significantly affect the speed of the hydrometallurgical process.
A metal matrix composite - consisting of a matrix of medium entropy alloy CoCrNi and Mo as reinforcement - is reported on the present study. The composite was produced by mechanical alloying (MA) in combination with spark plasma sintering (SPS).
The investigation of the microstructural features, chemical composition and basic mechanical properties of the bulk material were subject to study, by means of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray analysis (EDS) and Vickers microhardness testing.
A full-density composite has been achieved with the selected sintering conditions, within an average hardness of 520 HV0.3. Its' microstructure exhibited four different phases, possessing a matrix consisting of FCC solid solution reinforced by BCC particles surrounded by a Rhombohedral phase in the interface of the matrix/reinforcement and dispersed HCP precipitates.
Computed Tomography (CT) as a known medical research method is nowadays widely used in research institutions and production companies. Due to it’s non destrictive testing nature, CT finds application in both final product quality control such as castings or CNC machined parts and research of new materials, e.g. ceramics, composites etc. In aviation industry, one of the main factors in investment casting, crucial to quality of final product are properties and condition of ceramic moulds. Inspection is possible only after filling mould with molten alloy and breaking it after metal solidification. The purpose of article is to examine application of computed tomography in ceramic casting moulds quality control and investigation of certain ceramic pulp components effects on mold porosity and voids characteristics. Specimens in shapes of blocks and moulds in three geometrical configurations were prepared. Samples were produced using quartz, molochite and various binders. They were examined with micro and nano tomography. Test results were presented as high quality 3D models of specimens and percentage porosity. As a comparative method of obtaining porosity data, mercury porosimetry tests were carried out. ACKNOWLEDGEMENTS: The work done in the framework of a research project No. PBS3/A5/54/2016 funded by the National Centre for Research and Development.
The main goal of this study is show the effect of the advancing side (AD) and the retreating side (RT) position on the Residuals stress and local mechanical behaviors of dissimilar friction stir welds of aluminum alloys AA2024-T3 and AA7075-T6 were studied. Different samples were produced by varying the rotational speeds of the tool as 1200 and 1400 rpm and by varying the alloy positioned on the advancing side of the tool. we are Using Ultrasonic Method to Evaluate Residual Stress. This method is based on the acoustoelastic effect, which measure the velocity variation of the elastic waves according to the stress state of the material. This can be achieved through a calibration test to determinate the acoustoelastic coefficient (K). The results show a tensile stresses in the melted zone (MZ), heat affected zone (HAZ) and compression stresses in base metal (BM). The effect of the increase of the rotational speed is a reduction of the amplitude of the longitudinal residual stresses with a more reduction in the case where 7075 - T6 is in the Retreating side. This has been directly associated with increasing heat input and reducing thermal mismatch between different areas of the weld.
The effects of compressive and tensile pre-deformation among with further heat treatment on mechanical properties were investigated in extruded Mg-1Zn-Ca alloy. Mechanical properties and microstructure are notably influenced by a formation of twins during pre-deformation along the extrusion direction. However, the introduction of solute segregation and precipitation can reduce the impact of twinning on deformation by blocking of mobile twin boundaries. Thus, heat treatment, applied after pre-deformation, can improve mechanical properties of the extruded Mg alloy. Microstructure of samples before and after thermo-mechanical treatment was observed by scanning electron microscopy. The acoustic emission method was used to determine deformation mechanisms activated during deformation tests.
The production of synthetic tantalum concentrate (SynCon) in a multi stage pyrometallurgical process enables the use of various low grade input materials bearing at least a small Ta2O5 content. Thus, huge amounts of high melting slags accrue. For adequate product quality and process control the metal/slag separation is a crucial factor, wherefore the slag viscosity represents arbitrative indication. Slag composition and temperature are the dominating criterions regarding specification of slag viscosity. This study compares calculations of five established viscosity models (Riboud, NPL, Iida, Urbain and FactSage) for the analysis of their deviation at various temperatures regarding a slag enfolding the main components Al2O3, CaO, MgO, SiO2 and TiO2. Depending on the model in use the influence of the TiO2 concentration on the viscosity is more or less decisive and declines with rising temperature. For valid computations and experiments knowledge of the liquidus temperature is prerequisite. Measurements at necessary temperatures, typically higher than 1700 °C, are expensive and complicate since few appropriate (inert and heat resistant) crucible materials exist. Therefore, viscosity models are of great interest to generate fundamental data of liquid slags essentially needed for effective process development and improvement.
This paper presents the results of research on the possibilities of producing and using Cu / Al2O3 composite material fabricated by powder metallurgy. The starting materials for obtaining the composites were commercial powders: Cu and Al2O3. The quality of the combination of aluminum oxide with the matrix and the influence of aluminum oxide particles on sinter properties were also evaluated. Alumina was introduced into a copper matrix in the amount of 2.5 %, 5 %, 7.5 % and 10 % by weight. Before the sintering process, single pressing was performed with a hydraulic press at a compaction pressure of 620 MPa. The sintering process was carried out for 60 minutes at a temperature of 900 °C. The obtained sinters were subjected to the compaction process at a pressure of 620 MPa, and then again sintered at 900 °C for 60 minutes. The sintered compacts were subjected to the following tests: measurement of density, hardness, electrical conductivity and abrasion resistance. Observations of the microstructure on metallographic specimens made from the sintered samples were also performed using a scanning electron microscope (SEM). The process of compaction of the fabricated composite caused an increase in the hardness, density, electrical conductivity and abrasion resistance in comparison to a composite subjected to only the pressing and sintering process. Both the density and electrical conductivity decreased with the increase of Al2O3 content in composites after sintering and after the compaction process.
The synthesis and characterization studies of metal borides moved to center of both scientific and industrial interest in recent years due to their superior physical and chemical properties. Cobalt-nickel-boron based metal borides are technologically highly valuable boron-based materials with a high application potential in wide range of multi-functional areas due to their magnetic and catalytic properties.
In this study, an alternative route for obtaining crystalline binary and ternary metal borides was proposed at low temperatures using various chemical reaction types and media. The ternary system of Co-Ni-B was studied by using anhydrous metal chlorides and sodium borohydride powder mixtures. The reactions were carried out in a vertical furnace under flowing argon or in a sealed reactor under autogenic pressure, placed in a chamber furnace. The unwanted chloride phases were removed by hot water leaching after reaction. Some of the purified powders were annealed at 1100°C to improve the crystallinity. Effects of different reaction conditions (e.g. temperature, time, under Ar or under autogenic pressure) on the formation and microstructure of the final powders were investigated. Phase, chemical, microstructural, thermal characterizations and particle size measurements of the synthesized and annealed powders were conducted using X-ray diffractometer (XRD), X-ray fluorescence spectrometer (XRF), scanning electron microscope (SEM/EDX) and Zetasizer dynamic light scattering technique. Semi-crystalline CoBx-NiBx composite powders were obtained at 750°C in a sealed reactor under autogenic pressure. Crystalline CoNiB ternary borides were achieved after a reaction at 750°C for 2 h under Ar atmosphere and annealing at 1100°C for 6 h.
An important role in the investment casting process is played by the surface condition of the first coating of a multi-layer ceramic mould, as it directly affects the quality of the obtained cast. In industrial conditions, it is not possible to assess surface quality of the first ceramic mould cover without breaking it. The paper presents the analysis of the structure and surface roughness tests results of the first model coatings of model and production ceramic moulds. Ceramic moulds were made of 7 coatings. Three different ceramic mixtures were used to make them, differing in the used filler (molochite, quartz) or binder (Remasol aqueous binder, hydrolyzed ethyl silicate, Ludox water binder). Samples of industrial moulds were obtained by breaking them while model moulds in the form of rectangular shaped samples were made in specially designed wax dies. Model and production moulds were heat treated at 850°C, 900°C and 950°C, and then the roughness of the first coating was tested using the WYKO NT9300 optical profilometer. Samples were also subjected to microscopic examination to determine the structure of the model layer and the cross-section of the moulds. The research allowed to obtain the results of the impact of materials intended for moulds and heat treatment on the quality of the model layer. ACKNOWLEDGEMENTS: The work done in the framework of a research project No. PBS3/A5/54/2016 funded by the National Centre for Research and Development.
In this work, we introduce a numerical finite element model (FEM) describing the non-diffusional, displacive, reversible phase transformation in β titanium, which leads to the formation of stress-induced ω phase. The model calculates elastic strain energies in the vicinity of transformed ω particles at different applied stresses. The aim of the work is to predict at which circumstances will the activation of stress-induced ω phase transition be energetically favorable. In that case, the ellipsoidal ω particles can occur instead of the ω laminates. According to the model, with increasing external load the elastic strain energy in the material exhibits larger increment for ellipsoidal particles than for the laminates. Therefore, at certain stress values, the occurrence of laminates is favorable due to the lower strain energy. This result corresponds to the experimental investigations where stress-induced ω phase forms at certain applied stresses.
The as-cast Al-Zn-Mg-Cu-based alloy with and without Sc,Zr-addition was studied during isochronal annealing from room temperature up to 480 °C. Precipitation reactions were studied by differential scanning calorimetry and microhardness measurements. These measurements were compared to microstructure development that was observed by scanning electron microscopy. Microstructure observation proved eutectic phase at grain boundaries in the as-cast state of both alloys. The measurements of positron lifetime (LT) spectroscopy confirm the presence of Guinier-Preston (GP) zones in the initial state of both studied alloys. Neither structure nor volume fracture of eutectic phase shows changes after annealing up to 480 °C. The distinct changes in microhardness curves as well as in heat flow of the alloys studied are mainly caused by dissolution of GP zones and by formation of the particles of Al-Zn-Mg-Cu system. The apparent activation energy values of the thermal processes were calculated. The hardening effect after isochronal annealing at temperatures above ~ 300 °C reflects the Sc and Zr addition
Sintered permanent magnets based on the Nd2Fe14B intermetallic compound are widely used in industry as a rule in a temperature range of from -60 to 150 °C. However, in recent years, there appears a need to use such magnets at cryogenic temperatures and mainly at liquid nitrogen temperature (77 K). The natural increase in Br of Nd-Fe-B magnets with falling temperatures is well known phenomenon but is limited to temperatures above 135 K due to the spin-reorientation in Nd2Fe14B-based alloys. At this temperature, the easy-axis magnetic anisotropy changes to easy-axes cone anisotropy. The Pr2Fe14B compound exhibits no spin-reorientation transition up to cryogenic temperatures.
Because of this, permanent magnets based on (Nd,Pr)2Fe14B compound are of interest for investigators owing to the capability of these magnets to remain high hysteretic parameters at low and cryogenic temperatures. In this case, the natural increase in the hysteretic parameters with decreasing temperature can be adequately used.
The Pr2Fe14B-based magnets (Pr-Fe-Ti-Al-Cu-B) were prepared by traditional powder metallurgy technology, and 3 wt % HoH2 was added to the main powder at the fine-milling stage. The structure of the magnets was studied in detail by scanning electron microscopy (SEM/EDX) and the formation of pronounced so-called “core-shell” structure was demonstrated. The effect of HoH2 hydride addition on the hysteresis loop parameters of sintered Pr-Fe-Ti-Al-Cu-B magnets was studied and the marked improvement of hysteretic parameters was found. Domain structure of the magnets was studied perpendicular and parallel to the magnet texture using magnetic force microscopy. The data obtained indicate the well-formed magnetic texture. The average domain width is 1.2-1.8 µm.
ACKNOWLEDGEMENTS: This study was supported by the Ministry of Education and Science of the Russian Federation, agreement no. 14.616.21.0093 (unique identification number RFMEFI61618X0093) and the Ministry of Education, Youth, and Sports of the Czech Republic, project no. LTARF1803.
Using aluminum bronze and titanium foils, CuAl10Fe3Mn2-intermetallic phases laminated composites have been fabricated through reactive bonding at 875°C in vacuum. Investigations were concerned with the structural transformations of a bronze-Ti couple boundary. Holding for a few minutes resulted in the formation of a thin layer at the interface. Prolongation of the heating time lead to reactions in the liquid state and completely disappearing of titanium layers. Thus, the final microstructure consisted of alternating layers of intermetallic layers and unreacted CuAl10Fe3Mn2 bronze. The microstructure was revealed in optical and scanning electron microscopy (SEM). The study exhibited the presence of different reaction products in the diffusion zone and their chemical compositions were determined by X-ray microprobe analysis. The occurrence of different intermetallic compounds such as TiCu, Ti2Cu, τ1 (TiCu2Al) and τ2 (TiCuAl) was predicted from the ternary phase diagram Al-Cu-Ti. The predominant part of the intermetallic layers was the mixture of TiCuAl and TiCu2Al phases, since a liquid front of reaction was moving into the aluminum bronze. The microhardness of the reaction products and the elemental components was comparatively measured.
Evolution of microhardness during isochronal annealing up to 600 °C was studied in strips processed from Al-Mg-Sc-Zr alloy. Specimens for all measurements were prepared from conventionally mold cast and hot rolled strips (CC) or from strips after twin-roll casting (TRC). Selected TRC specimens were further either hot rolled or constrained groove pressed. The role of strips preparation methods on microhardness and annealing response was established. It was shown that the formation of coherent Sc and Zr-rich particles at temperatures close to 300 °C results in a significant increase of microhardness in specimens that have not been exposed to elevated temperatures during the preparation of strips. The highest microhardness was observed in CC materials as a result of a combined effect of fine grains and strengthening particles. Above 350 °C a degradation of mechanical properties occurs in two stages in all materials independently on their previous history. The observed drop of microhardnes was caused by the overaging of strengthening particles and withdrawal of the strengthening effect of the deformation structure.
The concept of semi-direct recycling rests on the selective leaching of the binder metals (commonly Co) by hydrometallurgical methods. This way, the hard phase (WC, TaC, NbC, TiC) ideally remains unaffected and forms a carbide skeleton, which can be reused in a powdered form for the fabrication of new substrates. Nevertheless, some portions of the carbides are dissolved. Hence, the aim of the present trials consists in disclosing the effects of binder content, TaC content (as cubic carbide) as well as grain size on the selectiveness of the binder leaching. For this, a statistical software (Modde 11) facilitates the compilation of a DOE, which eases the evaluation process. Other parameters like solution amount and concentration, temperature, test duration as well as substrate surface to liquid volume exhibit preferentially invariant conditions. Thereby, the results illustrate the implication of the substrate composition on the leaching behavior of cemented carbide in CH2O2 with H2O2.
We investigated aluminium (Al) and aluminum with 2 wt.% of magnesium (Al2Mg) salt-replicated microcellular metal foams. Salt-replication technique has proven to be a suitable method for the production of open-cell microcellular foams which differ in their mechanical properties from most other types of metal foams. We used sieved NaCl powders comprising of grains with average diameters of 25, 75, 150, and 400 µm. Samples were prepared by infiltration and consequent leaching of NaCl particles. Compression and digital image correlation (DIC) experiments were used to characterize the deformation behavior. It was confirmed by the DIC analysis that these foams have very low tendency to strain localization. Metal foams are one of the very few materials where size effects can be measured in bulk samples by conventional testing methods. The size effect was found in the plasticity of pure Al foams but not in Al2Mg foams. Al2Mg foams exhibit solid solution hardening and the Portevin-Le Chatelier effect. We propose that the PLC effect in Al2Mg foams might be due to the “chain reaction" of PLC strain bursts within the foam structural components (mostly struts) in a critical state.
The paper presents results of the physical modelling of the AlZn5,5MgCu aluminium alloy bars rolling process in the RSP14/40 three-high skew rolling mill. Investigations were carried out in the complexstrain state (simultaneous torsion and compression), by using the STD 812 torsion plastometer. Initial parameters were determinated during numerical modelling, by using Forge 2011® computer software. The purpose of the work was verification of the numerical modelling and physical representation of the rolling process in the three-high skew rolling mill. The scope of the research also included determination of the influence of the stock temperature on the flow stress changes, microstructure and microhardness of the invedigated material.
The as-cast AA5754 and AA6082 alloys with Sc,Zr-addition were investigated during isochronal annealing from room temperature up to 510 °C. Precipitation reactions were studied by electrical resistivity, hardness measurements and differential scanning calorimetry. The measurements were compared to microstructure development that was observed by transmission electron microscopy. Higher initial resistivity as well as hardness values are probably caused by a higher content of the solutes in the AA5754-ScZr alloy in comparison with the latter alloy. Both alloys contains spherical particles of the Al3(Sc,Zr) phase in the as-cast state. Moreover, the AA6082-ScZr alloy contains Mg,Si,Sc-containing phase at grain boundaries and rods/needles of the Mn,(Fe)-containing phase. The transient Al–Mg–Si-phase (β’’ and/or β’) particles formed during isochronal annealing in the AA6082-ScZr alloy cause a poor age hardening. The additional Al3(Sc,Zr) particles precipitation causes a pronounced hardening in the AA5754-ScZr alloy. The possible (weak) additional precipitation of the Al3(Sc,Zr) particles in the AA6082-ScZr alloy has a lower effect on hardness than the precipitation of β’’ and β’ phases or Sc and Zr solutes are probably bound in the Al3(Sc,Zr) particles and do not influence precipitation hardening in the course of isochronal annealing in the AA6082 alloy. The precipitation of the Al6(Mn,Fe)-phase was observed in the alloys during the isochronal heat treatment. The apparent activation energy values of precipitation of the transient β’’ and/or β’ phases, Al6(Mn,Fe)-phase and Al3(Sc,Zr) phase were determined.
Hot-compression tests of the alloys Ni-Al-Zr were performed.The tests were performed on the equipment Gleeble 3800 at 800 °C. The Ni3Al based alloys with different content of zirconium were tested in as-cast and directionally solidified state. Solidified samples were prepared from castings by Bridgman’s method. The alloys exhibit good values of yield strength and maximal achieved stress for this type of material. The alloys in directed state have better values of yield strength then as-cast alloys. The structure of alloys depends on the aluminum content. The alloys with 24 at. % Al are formed by phases Ni3Al and Zr-rich phase Ni5Zr. The hypostoichiometric alloys are formed by phases Ni3Al, (Ni) and Zr-rich phase Ni5Zr.
This paper represents the layer-by-layer synthesis results of the specimens obtained by laser cladding (LC) method. For basic material was used heat-resistant nickel alloy Inconel 625 constituting spherical shape powder. Process conditions of the LC was studied which are maintain the stable synthesis process. Structural study and mechanical test of specimens were carried out both after the manufacturing process and after the heat treatment process. Increasing of the mechanical characteristics possibility due to high-frequency vibrations during the synthesis process was studied.
The nitrides of Fe and rare-earth intermetallic compounds have attracted an increasing interest due to their unique magnetic properties and potential applications as permanent magnets. The recent investigations are associated with search of new hard magnetic compounds with lean rare-earth compositions. One focus was governed to the ordered compound a”-Fe16N2 for which as increased saturation as well a considerable anisotropy constant have been reported. The second, the RFe12N compounds that saturation could be higher than those of Nd2Fe14B while maintaining a comparable anisotropy field. The preparation of nitrides involves a number of difficulties. For example, it is not possible to obtain pure a”-Fe16N2 gas by nitrogenation because the solubility of nitrogen in austenite is less than the required 11.1 at. % per the established stoichiometry.
In the present work, the route of preparation for specimens by high temperature aging of preliminary pressed mixture (briquettes) of the Fe powder with differ nitride powders (BN, Si3N4, AlN) is suggested and the microstructure and magnetic properties of the synthesized alloys are studied.
The pressed briquettes from iron and nitride powders mixture in desired proportions were heated in the nitrogen atmosphere till temperatures of 1300-1550°C and held for 3 hours, and subsequently cooled along with the furnace. As a result of the solid or liquid-phase reaction within the sintering process, the ceramic is formed upon the heat-treatment of briquettes and the spherical metal fragments exudation on the surface of ceramic part of the briquette was observed. After aging the sample (Fe+33 wt.% BN) the composition of the spherical metallic fragment was comprised of 32 % Fe-48 % N-20 % B. The microstructure includes the eutectic structure between primary iron grains. The eutectic consists of Fe precipitates, as dendrites and the dark boride phase. In eutectics, the boride phase composition changes B from 19 to 24 at. % close to the stoichiometry of the metastable Fe3B compound. The microstructure of the metallic fragment of the sample (Fe + 30 wt.% Si3N4) consists of grains of the FeSi phase with composition 17 at. % Si - 83 at. % Fe. The microstructure of the metallic fragment of the sample (Fe + 22,5 wt.% AlN) consists of grains of the FeAl-based phase with composition 14,5 at. % Al - 70 at. % Fe - 15,5 at. % N. The obtained metal fragments are characterized by relatively high coercivity (0.50 kOe) comparable to those fine films and nanosized iron powders produced by gas nitrogenation.
Strain rate and temperature effects on Portevin-Le Chatelier (PLC) effect in coarse-grained AlMg, AlMgMnSc and AlMgMnZr alloys were investigated in this work. Tensile tests were carried out at temperatures ranging from 173 K to 423 K in an imposed strain rate range of 1×10-5 to 2.1×10-1 s-1. The coarse-grained alloys display a conventional sequence of types A, A+B and C when the strain rate or temperature are decreased or increased, respectively. It should be specified that types A and B dominate the overall pattern whereas type C serrations are only observed during short periods at the stage of necking at the left (low strain rate/high temperature) boundary of the PLC domain. The critical strains for the onset of the onset of the PLC at low strain rate were measured as s function of strain rate. Experimental dates are fitted according to the model proposed by Kubin and Estrin. The normal behavior was found for 223-248 K in AlMg alloy and for high temperatures in AlMgMnSc alloy. All these normal branches are stuck to the reference εc vs dependence for 298 K. On the one hand, the εc vs dependence shifts to the left when T is reduced from 298 K to 248 K, thus confirming the trend described above for the coarse-grained material. On the other hand, a backward shift is observed upon decreasing temperature down to 223 K for the AlMgMnZr specimen.
ACKNOWLEDGEMENTS: The study was financially supported by the Russian Science Foundation, under grant No. 17-72-20239.
The presented study deals with preparation and mechanical properties' investigation of powder metallurgy AlCoCrFeNiTi0.5 high entropy alloy, reinforced by homogeneous dispersion of TiC particles. Composite was prepared by the combination of mechanical milling and spark plasma sintering, analyzed by SEM, XRD, Vickers hardness and 3 point bending strength tests. TiC particles were formed by in-situ reaction of carbon introduced during mechanical milling process, and titanium present in the alloys' composition. The resulting material exhibited high levels of hardness (over 800HV) in addition to ultimate bending strength reaching 2 GPa.
The aluminum alloys, Al-1%Fe-0.3%Zr-0.25%Si and Al-1%Fe-0.3%Zr-1%Si, were investigated after hot rolling to a strain of 70% at 300 °C followed by annealing at 450 °C during 1 h. Hot rolling resulted in the elongation of initial grains along the rolling direction. The lamellar microstructure with the transverse size of structural elements of about 1 μm evolved during deformation. The hot rolling was accompanied by strengthening of the both alloys and an increase of the electrical conductivity in the Al-1%Fe-0.3%Zr-1%Si alloy due to Al3Zr particle precipitation. Annealing at 450 °C increased the yield strength to 170 MPa and 195 MPa for the Al-1%Fe-0.3%Zr-0.25%Si and Al-1%Fe-0.3%Zr-1%Si alloys, respectively. The fine structure after annealing contained dispersed particles with a size of about 5-10 nm, which were identified as Al3Zr. An increase in the electrical conductivity to 53% IACS confirmed decomposition of solid solution during annealing in the Al-1%Fe-0.3%Zr-0.25%Si and Al-1%Fe-0.3%Zr-1%Si alloys. The dispersion strengthening was discussed in term of interaction between dislocations and particles by the Orowan model and particle shearing.
The financial support received from the Ministry of Education and Science, Russia, (Belgorod State University Project No. 03.G25.31.0278) is acknowledged. The main results were obtained by using the equipment of the Joint Research Center, «Technology and Materials», Belgorod State University.
The paper presents investigation of the properties of joint region in the Mg/Al two layered material semi-finished product obtained by the explosion welding method. Aluminum alloy 1050 and magnesium alloy in the grade AZ31 were used to make the material to be analyzed. Two layered Mg/Al materials were made by using different technological parameters of explosion welding. In this work was made an analysis of microstructure changes and the microhardness distribution on the cross-sections of the stock materials. There were also made tests of layers connections quality by determining the maximum shear stress on the joint boundary. The results of the research show a significant deviation in microhardness distribution in the both layers near the joining border. Analysis of the results shows that for all used parameters of the explosion welding method guarantee a permanent connection of the both magnesium and aluminum layers.
The constantly growing amounts of industrial waste containing metals (electronic waste, dust, slime, used batteries, etc.) along with the fact the natural resources, especially the critical metals, are gradually running out, give the particular significance to the attempts of metal recovery.
The work presents the results of research into the method of zinc recovery from industrial dust by means of the combined hydro- and pyrometallurgical methods. The research scope included leaching, electrolysis, and thermal processing of the obtained products. The quantitative analysis of the obtained alloy was made.
Nowadays, manufacturing of materials with unique properties is in the center of attention of materials engineering. Aluminum and aluminum alloys are widely applied in variety of industries due to their high specific strength and in the following years they will become even more important. Construction elements made from aluminum and its alloys are produced mainly by casting or plastic working processes. In order to obtain the highest mechanical properties in afore mentioned materials their microstructure must be characterized by grain size on the level of sub or nanoscale. This goal can be achieved on several ways including SPD methods or by applying more unconventional methods such as rapid solidification. In this paper mechanical properties and results of microstructure observations of AlSi5 and AlSi10 has been presented. Materials were obtained by two different methods. At first traditional casting followed by hot extrusion at the temperature of 400°C was applied. The second manufacturing method was rapid solidification. In this case melted aluminum was casted on cold, fast rotating cooper wheel followed by plastic consolidation by hot extrusion. From obtained rods samples were cut for tensile test as well as microstructure observations which were performed both with a use of light and electron microscopy. Microstructure examination results and mechanical properties confirmed that rapid solidification significantly increases mechanical properties by structure refinement.
The influence of heat treatment on microstructure and deformation behaviour of Zn-based magnesium alloys with an addition of Ca and Nd was investigated. The Mg alloys were prepared by a modified gravity casting process with directional solidification by lowering the crucible into a water bath. After machining, the billets were solid-solution annealed for 20 h at 400°C and thereafter indirect extruded to a round bar (extrusion ratio 1:25, a final diameter of 10 mm) with an extrusion speed of 0.5 mm/s (ram speed, corresponding profile exit speed 0.75 m/min). The homogeneity of the extruded rods was determined by light microscope (LM) perpendicular to the extrusion direction. Vickers hardness test was performed on cross sections of samples, which were heat treated for various times to find peak aged conditions. Changes in microstructure were investigated by electron back-scattering diffraction method (EBSD) in scanning electron microscope (SEM). The as-extruded and annealed samples were tested under compression along the extrusion direction at room temperature (RT). Acoustic emission (AE) signals, recorded during deformation tests, gave us information about active deformation mechanisms during plastic deformation.
The quasilongitudinal US velocity v, elastic module E001, “fast” quasitransversal US velocity v┴[100], shear module G100, Poisson coefficient μ, Debye temperature θD were determined. Measuring of IF background Q-10 after different heat, mechanical, radiation treatments gave information about the changing of the thermo-elastic strains fields in Ag-Zn, Al, Ti alloys.
The growth of heights IF maximums QM-1 testified the growth of structural defects, concentration, and the broadening of IF maximums ΔQM-1 represented the relaxation process of structural defects of new types in Ag-Zn, Al and Ti alloys. The correlation between elastic module Е, pressure p and temperature Т may be presented as surface (“directional surface of elasticity body”) before and after satiation, which gives additional information about influence of the saturation of solution.
Phase change materials (PCMs) are now a well-established category of materials for thermal energy storage. The absorption and release of latent heat during the solid-liquid phase change is employed to store thermal energy in case of the PCMs. Most PCMs need to be hermetically sealed in a container or a tank because of the risk of leakage to the surrounding environment when a PCM is in the liquid state. A good compatibility of the PCMs and the materials of container is very important for the long lifespan and safety of the heat storage systems with PCMs. Metals are excellent heat conductors and for this reason they are often used as encapsulation materials for the PCMs. The present paper focuses on the methodology and the results of the compatibility tests of two organic-based PCMs and two inorganic-based PCMs with metals. Three sets of metallic samples of encapsulation materials have been prepared. The first set contained copper samples, the second aluminium samples and the third stainless steel samples. The samples were immersed in the PCMs creating metal-PCM pairs and subjected to periodical heating and cooling in a small environmental chamber. This process mimicked the operation of thermal energy storage. One sample of each metal-PCM pair was withdrawn from the testing every week and examined in order to monitor the progress of corrosion and other changes. The paper presents the results of the tests.
Aluminum alloys, due to their very good strength properties, are used to produce many important structural elements. The AW-7020 stop is mainly used in weldment elements, cranes, hoists, beams, roof construction elements and windows. The wide use of these materials encourages the search for methods to monitor damage and locate the places where they occur. The article uses the acoustic emission method to detect damage in AlZn4.5Mg1 aluminum alloy. In the experimental part, a static tensile test was carried out with simultaneous recording of vibrations of the loaded material by means of a connected acoustic-electric sensor. The received signal was then further processed and was used to generate electrical signal value plots (URMS) as a function of time. These plots were applied to the corresponding stretching curves. The obtained results allow to state that the acoustic emission method can be successfully used to detect and perhaps locate damage in aluminum alloys. This can contribute to the diagnosis of structural damage during their operation.
The practical use of FeAl intermetallic alloys will be possible in a wider range after the development of not only the technology of making permanent joints, but also after determining their physicochemical properties. In the work, the surface condition of the TIG welded intermetallic FeAl alloy was oxidized in air at 900 and 1000 ° C. Differences in the surface state of welded Fe40Al5Cr0.2TiB alloy were shown depending on its area, in particular in the weld area and the weld boundary. The test material was the welded joint of the Fe40Al5Cr0.2TiB intermetallic alloy obtained by melting the solid material after casting. Next, microstructure analysis was performed using light microscopy, scanning electron microscopy and hardness measurements before and after oxidation. In addition, corrosion products were analyzed using XRD.
Recently, zinc and it is alloys have been investigated for use as biodegradable materials in a wide range of applications. For instance, in cardiovascular or orthopedic surgery. Extensive plastic deformation of ductile materials realized at elevated temperatures usually leads to dynamic recrystallization and, at suitable conditions, to refining of microstructure. In this way, the usability of pure metals with insufficient mechanical characteristics can be achieved. This work is focused on preparation of zinc wires by one-step hot extrusion at various temperatures. Precursors (6 mm in diameter) with various grain size were extruded to 250 µm diameter and the extrusion ratio was 576. Microstructure and texture of materials were characterized by scanning electron microscopy and electron backscattered diffraction. Tensile properties of the prepared wires were also measured.
The main purpose of this study is to find the influence of the grain size of the initial zinc precursors and extrusion temperature on microstructural and mechanical characteristics of the prepared wires.
The authors would like to thank Stanislav Habr for performing of the extrusion process and to the Czech Science Foundation for the financial support of this research (project no. 18-06110S).
Additive manufacturing offers great potential for producing metal parts with a high degree of geometrical complexity and high mechanical properties. However, the number of alloys in the form of powder material that can be applied in these technologies are limited at the moment. A solution for this problem might be found by utilizing a mechanical mixture of elemental powders for manufacturing parts by laser additive manufacturing which would result in the in-situ synthesis of the required alloy.
This work presents the results of the study of the in-situ synthesis of Ti-5Al, Ti-6Al-7Nb and Ti-22Al-25Nb alloys by laser additive manufacturing, i.e. selective laser melting (SLM) from elemental powders. Titanium, aluminum, and niobium powder particles were used as initial powders, which were mechanically mixed to prepare powder mixtures of the corresponding alloys. It was shown that SLM technology can be successfully utilized to synthesize α-titanium Ti-5Al alloy from elemental powders with homogeneous chemical composition and high mechanical properties. In order to fully dissolve niobium particles and achieve a homogeneous chemical composition and microstructure of Ti-6Al-7Nb and Ti-22Al-25Nb alloys heat treatment of bulk samples after SLM is required. The microstructure, phase composition of the obtained material before and after different heat treatments were studied, also the mechanical properties of the obtained alloys were investigated.
In recent years, the application of various additions (hydrides, oxides, intermetallic compounds, etc.) in powder mixtures for manufacturing Nd-Fe-B magnets shows promise as the method that allows one to increase the hysteretic characteristics of the magnets at the expense of realized grain-boundary diffusion and grain-boundary structuring processes. The processes allow one to introduce both the heavy rare-earth metals and copper that was shown also to favour the increase in the hysteretic parameter of Nd-Fe-B-based compositions. In the present work, we consider the alloys Tb3(Co1-x,Cux) with x = ~0.4 as additions to Nd-Fe-B-based powder mixtures. The alloys were prepared by arc melting in an argon atmosphere and subjected to homogenizing annealing at 600 °C for 90 h. The phase composition and phase equilibria in the system were studied by X-ray diffraction analysis, DTA, optical and scanning electron microscopy, electron microprobe analysis, and low-temperature thermal magnetic analysis The composition was shown to be three-phase, Tb3(Co,Cu), Tb12(Co,Cu)7, and Tb(Co,Cu) that is the primarily solidified phase in the system. The copper solubility in the Tb3Co and Tb12Co7 compounds and cobalt solubility in the TbCu compound were determined. A portion of the isothermal section of the Tb-Co-Cu system with at 600 °C was constructed. The possibility of the hydrogenation of the Tb3(Co1-x,Cux) composition with x = ~0.4 with the formation of TbHx, Co, Cu was demonstrated.
ACKNOWLEDGEMENTS:This study was supported by the Ministry of Education and Science of the Russian Federation, agreement no. 14.616.21.0093 (unique identification number RFMEFI61618X0093) and the Ministry of Education, Youth, and Sports of the Czech Republic, project no. LTARF1803.
The article presents the results of pilot tests used in the industry of abrasive diamond segments, made on various metallic binders in powder metallurgy technology, intended for grinding granite surfaces. The article presents the results of testing the hardness of abrasive segments using the Brinell method. The examined segments are characterized by different hardness - 86.33 HB and 101 HB. The impact of hardness of segments on their ability to maintain diamond grain in the binder was noticed, which translated into wear of abrasive segments during their work. Tribological tests were carried out for their wear during operation (research cycles), determined by the loss of mass of abrasive segments in the process of grinding the granite surface of the Strzegom type, with given kinematic parameters and constant clamping. Research on the wear of diamond segments was carried out on the author's own research stand. Designed and done special holder for fixing abrasive segments for a table drill was designed and made, which enables fixing them in a non-destructive manner. The tribological tests were carried out taking into account the factors of surface parallelity of the diamond segments to the work surface (granite slab) and at the axial pressure (perpendicular) to the surface being worked. A detailed description of the test stand is discussed in the full text paper. The article presents the results of microscopic observations of the examined segments after each research cycle, using a metallurgical microscope in the inverted system of the Nikon Eclipse MA200. The cognitive goal of the research was to broaden the current knowledge on the properties of abrasive segments during their work and to examine the changing structure of the diamond segment matrix in the cyclic work process.
The SHS method was used to synthesize Ti – Si intermetallic phases. The samples were fabricated by mixing Ti and Si powders with proportions corresponding to Ti3Si, Ti5Si3, Ti5Si4, TiSi and TiSi2 phases. The XRD method was used to analyze the phase composition. The process resulted in the formation of Ti5Si3, Ti5Si4, TiSi and TiSi2 phases. A Ti3Si phase did not occurre in any produced specimens. XRD analysis showed that specimen can react with graphite mold, creating the phases that contain carbon. Effect of Ti particles granulation on the phase composition was also analyzed. The results for several samples containing coarse-grained Ti particles showed that this element has not reacted completely, while the reduction of the granulation led to complete reaction.
The metallurgical production of ferronickel in the electric arc furnace provokes large amounts of slag with strong acidic character and high melting points, which seriously stresses the furnace refractory lining. In this study corrosion mechanisms have been investigated between high magnesia refractory substrates and synthetic FeNi slags in a hot stage microscope up to 1650 °C. The materials taken into consideration comprised a simple synthetic slag, mixed from specific pure oxides, similar to those from ferronickel producers. The experiments proceeded under a controlled gas atmosphere of 60 % CO and 40 % CO2 that simulates the relevant process conditions. The corrosion mechanisms of each system were determined by SEM analyses. The obtained results indicated that slag corrosion is dominating with a pronounced partial dissolution of refractory. Spot analyses show that iron diffuses into the magnesia grains, which transform to magnesiowustite meanwhile SiO2 forms different types of olivine like forsterite and monticellite. Finally, the comparison of these findings with those predicted by thermodynamic calculations indicated the corrosion mechanisms and draw implications for improving the refractory performance.
In 2018 it is 150 years since D.K. Chernov, the metallurgical science expert, made the report on the results of the research of the Fe-C alloy samples and ingots and for the first time ascertained the presence of the critical points, i.e. phase transitions. The work of D.K. Chernov served as the beginning of the construction of the iron-carbon diagram. A great amount of research on the construction and specification of the iron-carbon phase diagram has been carried out during the past period.
In the present work a critical analysis of the generally recognized combined iron-carbon and iron-cementite diagram is given, theoretical and experimental investigations by studying the microstructures of the iron-carbon alloy samples quenched from various temperatures have been carried out. Based on the research, a full equilibrium phase diagram of the iron-carbon system has been constructed, in which the non-variant three-phase equilibrium ferrite+graphite↔cementite at the temperature 727 ºC, two-phase equilibrium ferrite+graphite in the temperature range 738 – 727 ºC and two two-phase regions ferrite+cementite (up to 6.67 % C) and cementite+graphite (more than 6.67 % C) at the temperatures below 727 ºC are present. It is shown that cementite cannot be formed in the iron-carbon alloys at the temperatures exceeding 738 ºC at high cooling rates. The author considers expedient not to use the version of the metastable iron-cementite phase diagram and to exclude the designation of the alloy microstructures (perlite and ledeburite) in the phase diagram.
Nd-Fe-B permanent magnets are key materials in the electric power system and indispensable for the future success of environmentally beneficial technologies. The hysteretic characteristics of sintered Nd-Fe-B magnets are highly sensitive to their microstructure and composition of phases. This paper is focused on the coercivity enhancement of the near-stoichiometric Nd2Fe14B-based magnet by the optimizing microstructure, which included processes of grain boundary diffusion and grain boundary structuring via the application of hydrogenated Tb3Co0.6Cu0.4Hx composition added to the powder mixture. The base alloy having the composition Nd-24.0, Pr-6.5, Dy-0.5, B-1.0, Al-0.2, Fe-balance was prepared by strip-casting technique and subjected to hydrogen decrepitation during heating to 270 °C in a hydrogen flow at a pressure of 0.1 MPa and subsequent 1 h holding at this temperature. The Tb3Co0.6Cu0.4 alloy was prepared by arc melting of starting components in an argon atmosphere on a water-cold copper bottom using a non-consumable tungsten electrode. The ingot was subjected to homogenizing annealing at 600 °C for 90 h and subsequent hydrogenation under the conditions used for the decrepitation of strip-casting alloy. Hydrogenated Tb3Co0.6Cu0.4Hx compound and hydrogen-decrepitated strip-casting alloy were mixed and subjected to mechanical activation. The microstructure, phase composition and REM, Co, Cu distributions for the prepared magnets were investigated by SEM/EDX method. It was found that the total REM content in the main magnetic (Nd, Pr, Tb)2Fe14B phase is ca. 30 wt.%. Intergranular Nd-rich phases differing in the Tb, Co, Cu contents were identified. Studies of the stability of structure-sensitive parameter, namely, the coercive force jHc of the sintered magnet prepared with 2 wt.% Tb3Co0.6Cu0.4Hx addition to the low-temperature heat treatments show the increase in the coercive force up to 1480 kA/m.
This paper presents a study of the effect of high voltage electrospark deposition (ESD) using tungsten electrode on the carbon steel. The layers were investigated with metallographic methods. Microscopic examination was carried out to examine the structure of formed layers. Image analysis methods were used to observe the cross-section of the layer. Scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX) analysis was conducted to characterize the microstructure and composition of the coating. Micro-hardness tests were carried out to evaluate the mechanical properties of coating on carbon steel. The results of investigations showed that there is a possibility of obtaining the satisfying quality superficial layer on the carbon steel C45 using tungsten electrode.
One of the mechanical alloying main advantage is a possibility to combine together different elements that are difficult or even impossible to combine by conventional melting methods due to their high reactivity in liquid or semi-liquid state. In the present work results of examinations performed on Al-AgO and Al-CeO2 composite rods obtained by mechanical alloying on the University of Nihon in Tokyo has been presented. As-extruded materials were subsequently subjected to structural observations (SEM/TEM) and X-ray diffraction analysis (XRD). Both composites were characterised by presence of intermetallic phases which forms at elevated temperature as a result of aluminium matrix and strengthening particles reaction. In order to determine composites thermal stability, samples were subjected to annealing in a wide temperature range (473K-873K). Changes in microhardness value after annealing has been determined and compared with composites properties obtained after extrusion. Behaviour of CeO2 and AgO strengthening particles in reactive matrix were analysed both after production process (MA, hot extrusion) and annealing treatment.
One of the currently used industrial methods of zinc and lead production is Imperial Smelting Process, based on the use of a shaft furnace. It was created for the processing of traditional minerals of both metals that form compounds with sulfur. Their processing involves the necessity of removing sulfur from the materials before applying them to the furnace. This task is carried out by a specially constructed sinter plant, which also prepares the furnace charge for physical and chemical properties. In recent years, the necessity has become the processing of increasingly-occurring post-production waste containing Zn and Pb on the market, in which the carriers of these metals are ZnO and PbO. These wastes are characterized by very diverse physical properties that negatively affect the sintering process and, as a consequence, the use of such wastes for sinter plant operation, and especially of the shaft furnace. The influence of these properties of materials on the agglomeration process and consequently the production effects of zinc and lead were analyzed. An industrial test was carried out to explain the influence of metal-bearing material size distribution on production effects such as fuel consumption, production, etc.
This thesis is aimed on study of microstructure and purity of the alloys with nominal composition of Ni-35Ti-15Zr and Ni-45Ti-5Zr (at. %). The alloys were prepared by plasma metallurgy processes. Metallographic samples were prepared from an edge and central part of the ingot because chosen type of preparation does not manage to reach composition homogeneity in a longitudinal axis of the ingot. An optical and scanning electron microscope were used for documentation of microstructure. In both cases, the microstructure was polycrystalline with random orientation of grains. Individual grains consisted of dendrites formed by the NiTi-phase. On the contrary, interdendritic space was rich with Zr, eventually, it contained undesirable inclusions of TiC and ZrO2. They form in consequences of chosen technology of preparation in combination with high melting temperature. Because titanium is significant picker, contents of oxygen and carbon were monitored in the ingot samples of both alloys. The Ni-45Ti-5Zr alloy contained of 0.115 wt. % O2 and of 0.013 wt. % C. For the Ni-35Ti-15Zr alloy, the content of O2 was 0.103 wt. % and content of C was 0.012 wt. %. Compared to industrially manufactured NiTi-based memory alloys, contents of both elements should not exceed C < 0.05 wt. % and O2 < 0.02 wt. %. We can submit, that chosen method of preparation – plasma metallurgy – did not prevent the oxidation of both alloys, even though the melts were in a protective atmosphere of Ar with a purity of 4N6. By contrast, the carbon content remained in the standard.
To study the effect of gadolinium content and grain size on the Mg-Gd binary alloy deformation mechanisms, a broad range of Gd concentrations (0.4 to 4.2%) and grain size (15 to 500 microns) were used. Acoustic in-situ emission was used to better understand deformation mechanisms.
In the present study, commercial pure titanium (Grade 2) was joined to the stainless steel (X5CrNi18-10) by diffusion bonding using different intermediate materials like aluminum, copper and nickel. The thickness of those filler metals were 100 μm. The use of intermediate materials to create diffusion bond minimize thermal expansion mismatch, reduce joining temperature and pressure, inhibit diffusion of undesired elements to the base materials. However it also can cause formation of numbers of intermetallic phases. The investigation focus on comparing the wear resistance of the obtained diffusion joints. The microstructure of the joints were investigated using scanning electron microscopy equipped with an energy dispersive X-ray system (EDS) to determine chemical composition of joint. The structures of the joints varied importantly depending on the interlayer. However in the samples obtained by nickel interlayer at the borders of materials were observed Kirkendall voids. Value of friction force and wear resistance of diffusion bonded joints were carried out by block-on-ring frictional pair, preformed on the tribological tester T-05. The study was carried out under conditions of technically dry friction for the concentrated sliding contact loaded with 300 N. Friction distance for each test was 400 m. The results show that The maximum values of friction coefficient and mass loss was obtained for joints with nickel interlayer.
Magnesium with Zr alloying element was processed by severe plastic deformation method – equal channel angular pressing (ECAP). The processing led to a significant grain refinement and better mechanical properties. The material was characterized using various experimental techniques, e.g. microhardness measurements and scanning electron microscopy with electron backscatter diffraction (EBSD).
Aluminium alloys show a high strength-to-weight ratio and a relatively good corrosion resistance making them prospective structural materials in many fields. In material standards of commercial Al alloys, chemical composition is always defined as concentration ranges of alloying elements and impurities. In some cases, concentration ranges allowed within one material grade are relatively wide. It can be expected that mechanical and corrosion properties of one material grade are also variable that can be problematic in some applications. The aim of this contribution is to demonstrate variations of mechanical and corrosion properties of several standardized grades of aluminium casting alloys.
Metastable beta titanium alloys are receiving much interest for various applications such as aircraft industry and medicine thanks to their good mechanical properties and biocompatibilty. In this study, binary biomedical Ti15Mo alloy was prepared by powder metallurgy. Gas atomized powder was milled in a cryogenic mill and sintered by field assisted sintering technique (FAST). Mechanical milling of powder particles significantly changes their shape and size due to intensive plastic deformation and grain refinement within each particle, which is also reflected on the increased microhardness. Initial (non-milled) and milled powders were sintered above and below beta-transus temperature of Ti15Mo alloy (740°C). The compaction of the powders was accomplished by short-time sintering in order to preserve fine-grained structure of material. The effect of milling as well as the parameters of sintering were investigated. The microstructure of the milled powders after sintering revealed lower porosity and increased volume fraction of α-phase particles when compared to non-milled powder sintered under equivalent conditions.
The residue salt slag produced during the melting-process (recycling-process) of the lightweight-metal magnesium - a mixture of several covering salts, metal oxides and metallic components - must either be dumped or processed. A new chemical process is now in development for this type of dangerous waste. The aim of this process development is to extract the reusable salts from the magnesium-containing residues and to convert the residual solid fraction into a high-quality tradable product by acidic digestion. The proportion of the resulting inert residue of the recycling process should be as low as possible. Another important aspect of the concept is the use of the low-temperature thermal energy generated during the leaching process.
A fine-grained alloy with a composition of Ti-48Al-2Nb-2Cr (at. %) was prepared by Self-propagating High temperature Synthesis. The relationship among different compression ratio, microstructure, porosity, density, mechanical properties and residual stresses of Ti-48Al-2Nb-2Cr alloy was studied by scanning electron microscopy, X-ray diffraction, neutron diffraction and mechanical testing. It was observed, that during compression the processes of hardening as well as increasing of residual stresses take place. The residual strains and stresses in bulk of the material were calculated.
This work presents an application of Abaqus simulation software based on Finite Element Method in pressure pulse test simulation to optimize design of Charge Air Cooler and prepare it for serial production release. The work explains step by step how the pressure pulse test simulation of Charge Air Cooler design is performed on a level of virtual validation and what kind of useful information it can provide to the development team. Most of all this work, based on the example of Charge Air Cooler, shows how a big role play simulation software today and how it can improve the product and reduce development costs.
Mechanical properties of ultra-fine grain magnesium alloys AE42 and LAE442 prepared by ECAP were investigated. The study was focused on finding suitable conditions for the superplastic deformation. In the first place, the thermal stability of the microstructure was investigated. Afterwards, the strain rate sensitivity was measured in the temperature range 180-240 °C and the strain rate of ε`=5·10-5 - 2·10-3 s-1. Conditions for tensile tests of ε`=10-4 s-1 and ε`=10-3 s-1 at 180 °C and 240 °C ware selected. Finally, the microstructure change as a result of deformation was observed by AFM and EBSD.
The results of corrosion resistance in neutral salt spray of aluminum alloy 5754 used as a construction material in the automotive industry has been presented in the paper. The samples of aluminum alloy were exposed to 5% NaCl, neutral salt spray according to ISO 9227: 2017 and the following methods: linear polarization, potentiodynamic cyclic voltametry according to PN-EN ISO 10271: 2012 and impedance spectroscopy according to PN-EN ISO 16773: 2009. In order to correlate the tests as a corrosive environment at temperature 35°C, 5% NaCl neutral salt solution was used. Obtained results have been developed in terms of corrosion mechanism, extension and type of corrosive environment. It has been found that tested material is resistant to corrosion in a 5% NaCl neutral corrosion environment. The aluminum alloy 5754 has good corrosion resistance properties which are required for many structural components in the automotive industry.
Aluminum alloy 5754 has a high welding and strength properties and also an excellent resistance to atmospheric and marine corrosion. The alloy is used in many industries e.g. automotive, railway, marine building, electricity, chemistry and forging. In this work, strength properties of aluminum alloy 5754 after a salt chamber have been investigated. To the experiment strength tests samples made of 5754 aluminum sheet were exposed to neutral and acidic (with the addition of CuCl2) salt spray. The exposure was performed suitably at a temperature of 35°C and 50°C and samples were periodically drawn out from the corrosion chambers at every 7 days and every day hours during coursing of experiment. The corroded samples were subjected to testing of strength properties (Rm, Rp0.2, A50) according to EN ISO 6892-1: 2016. It can be concluded, that after CASS Test of Al 5754 alloy, the plastic elongation A50 showed the greatest decrease (up to 50%). In conclusion, a long-term use of Al 5754 alloy in salt corrosion enviroment may cause their previous consumption as a result of significant reduction of strength properties.
Aluminum dross consists of a heterogeneous mixture of large lumps, fine oxides and metal pieces. Consequently, sampling requires considerable experience and effort. Additionally, the skimming procedure of the melt, alloy composition, type of fluxing agent and the cooling method of the dross control the present amount of free-metal in the dross. In industrial practice, the formed dross in the aluminum smelter is regularly removed and a part of the liquid metal can be squeezed out. Subsequent, the tilting drum furnace recovers most of the aluminum from the dross with assistance of a crumbly salt slag. In contrast, the present study applies a liquid salt slag with a higher salt factor than in industry. Thereby, the higher amount of salt decreases the number of large lumps from aluminum-particles in the slag and the metal yield displays higher values. For this purpose, experiments in the top blown rotary converter at the Chair of Nonferrous Metallurgy (Montanuniversitaet Leoben) take place. Then, the recovered portion of the experimental technique is compared to the industrial method. Finally, an economic calculation exhibits the feasibility of improvements in the process. Supplementary, the metal amount in the dross can be quantified reliably.
Paper presents characteristics of thermovision, 3D scanning and tomography methods used for quality rating in multilayer ceramic moulds used for purposes of aircraft turbine blades casting. Moulds measurements were performed with thermovision camera, 3D scanner and tomography. Results were converted via dedicated software for each method and were saved in compatible file format that allowed to perform an analysis. One of the decisive factor of these measurement methods usefulness are accuracy and measurement error. For obtained measurement results quality rating selected statistical methods, Measurement System Analysis MSA and R&R index were used. Analysis allowed to estimate uncertainty and efficiency for applied non-destructive measurement systems for multilayer ceramic moulds rating. ACKNOWLEDGEMENTS: The work done in the framework of a research project No. PBS3/A5/54/2016 funded by the National Centre for Research and Development.
The contribution deals with the determination of the influence of the micro geometry of the cutting tool on the progress and size of the dynamic load of the system in the machining process. The experimental part was realized in conditions of longitudinal turning of aluminium alloy EN AW 2014. For machining alloys were suggested replaceable cutting inserts with pre-set micro geometry edge with mark CCGT 120408-AL and cutting conditions. By means of the mechanical adjustment of the micro geometry of brushing, the rounded edge was achieved for radius 0-5 μm, 10-15 μm and 20-25 μm for tested inserts. During the experimental activity of machining aluminium alloy, the dynamic load of the system was measured and evaluating for the effect of the individual parts of the cutting forces using the stationary piezoelectric dynamometer Kistler. The resulting cutting force was determined with respect to the radius of the rounded edge and the value of the feed rate of the cutting tool.
Experimental description of the Al-Cu binary phase diagram is presented in this study. The Al-Cu binary system has been investigated intensively by experimental or theoretical approach as a key binary for many Al-based, Cu-based, and dural alloys. For the phase diagram investigation, a combination of dynamic and static analytical methods was used. The characterization of phase composition of long-term annealed samples was done by X-ray powder diffraction (XRD) at room temperature or at higher temperature (HT-XRD). Metallographic investigations and chemical phase and overall composition analysis were performed by scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM-EDX). Temperatures of phase transitions were measured on high-temperature DSC heat flow. Congruent melting of the theta-phase was observed. Phase boundaries of several intermetallic phases was corrected in comparison with older published results.
The paper presents the results of research aimed at the use of thermal imaging as the method of assessing changes in the structure of multi-layered ceramic forms, intended for the investment cast parts of air blades. Analysis of infrared radiation allows to notice anomalies resulting from incorrect temperature distribution, which, in combination with other methods of quality control, creates the possibility of developing an innovative system for monitoring unit processes of producing jet engine components. FLIR T640 thermal camera and dedicated FLIR software was used for the tests. The molds were heated in a laboratory dryer to the temperature of about 200℃, and then changes in radiation intensity were registered. The image generated by the camera served as input for analysis with use of Research IR software. As a result, of research and analysis, the relationship between the thickness of the molds wall and the percentage decrease in temperature over time was determined and a comparative analysis of thermal images with prepared castings of the blades was carried out in order to detect visible real defects. The paper presents also innovative test bench, which feature is active thermovision equipment. Test stand was used to create comparison analyze between thermo-images from passive and active laboratory tests. Results of these tests lead to continuation of research in field of using thermovision methods as a new way to check quality of multi layered ceramics molds. ACKNOWLEDGEMENTS: The work done in the framework of a research project No. PBS3/A5/54/2016 funded by the National Centre for Research and Development.