Subjects -> METALLURGY (Total: 59 journals)
Showing 1 - 10 of 10 Journals sorted alphabetically
Acta Metallurgica Slovaca     Open Access   (Followers: 2)
Advanced Device Materials     Open Access   (Followers: 6)
American Journal of Fluid Dynamics     Open Access   (Followers: 44)
Archives of Metallurgy and Materials     Open Access   (Followers: 9)
Asian Journal of Materials Science     Open Access   (Followers: 4)
Canadian Metallurgical Quarterly     Hybrid Journal   (Followers: 21)
Complex Metals     Open Access   (Followers: 2)
Energy Materials : Materials Science and Engineering for Energy Systems     Hybrid Journal   (Followers: 24)
Graphene and 2D Materials     Open Access   (Followers: 6)
Handbook of Ferromagnetic Materials     Full-text available via subscription   (Followers: 1)
Handbook of Magnetic Materials     Full-text available via subscription   (Followers: 2)
High Temperature Materials and Processes     Open Access   (Followers: 6)
Indian Journal of Engineering and Materials Sciences (IJEMS)     Open Access   (Followers: 11)
International Journal of Metallurgy and Alloys     Full-text available via subscription   (Followers: 2)
International Journal of Metals     Open Access   (Followers: 7)
International Journal of Minerals, Metallurgy, and Materials     Hybrid Journal   (Followers: 12)
International Journal of Mining and Geo-Engineering     Open Access   (Followers: 4)
Ironmaking & Steelmaking     Hybrid Journal   (Followers: 5)
ISIJ International - Iron and Steel Institute of Japan     Full-text available via subscription   (Followers: 26)
Izvestiya Vuzov. Poroshkovaya Metallurgiya i Funktsional’nye Pokrytiya (Proceedings of Higher Schools. Powder Metallurgy аnd Functional Coatings)     Full-text available via subscription   (Followers: 2)
JOM Journal of the Minerals, Metals and Materials Society     Hybrid Journal   (Followers: 35)
Journal of Advanced Joining Processes     Open Access  
Journal of Central South University     Hybrid Journal   (Followers: 1)
Journal of Cluster Science     Hybrid Journal  
Journal of Heavy Metal Toxicity and Diseases     Open Access  
Journal of Iron and Steel Research International     Hybrid Journal   (Followers: 11)
Journal of Materials & Metallurgical Engineering     Full-text available via subscription   (Followers: 2)
Journal of Materials Processing Technology     Hybrid Journal   (Followers: 21)
Journal of Metallurgical Engineering     Open Access   (Followers: 4)
Journal of Sustainable Metallurgy     Hybrid Journal   (Followers: 3)
Materials Science and Metallurgy Engineering     Open Access   (Followers: 7)
Metal Finishing     Full-text available via subscription   (Followers: 20)
Metallurgical and Materials Engineering     Open Access   (Followers: 7)
Metallurgical and Materials Transactions A     Hybrid Journal   (Followers: 42)
Metallurgical and Materials Transactions B     Hybrid Journal   (Followers: 32)
Metallurgical and Materials Transactions E     Full-text available via subscription   (Followers: 2)
Metallurgical Research & Technology     Full-text available via subscription  
Metallurgical Research and Technology     Full-text available via subscription   (Followers: 8)
Metallurgy and Foundry Engineering     Open Access   (Followers: 3)
Mining, Metallurgy & Exploration     Hybrid Journal  
Powder Diffraction     Full-text available via subscription   (Followers: 1)
Powder Metallurgy     Hybrid Journal   (Followers: 35)
Powder Metallurgy and Metal Ceramics     Hybrid Journal   (Followers: 7)
Powder Metallurgy Progress     Open Access   (Followers: 5)
Practical Metallography     Full-text available via subscription   (Followers: 6)
Rare Metals     Hybrid Journal   (Followers: 3)
Revista de Metalurgia     Open Access  
Revista del Instituto de Investigación de la Facultad de Ingeniería Geológica, Minera, Metalurgica y Geográfica     Open Access  
Revista Remetallica     Open Access   (Followers: 1)
Russian Metallurgy (Metally)     Full-text available via subscription   (Followers: 4)
Science and Technology of Welding and Joining     Hybrid Journal   (Followers: 8)
Soldering & Surface Mount Technology     Hybrid Journal   (Followers: 2)
Steel Times lnternational     Partially Free   (Followers: 19)
Transactions of the IMF     Hybrid Journal   (Followers: 14)
Transactions of the Indian Institute of Metals     Hybrid Journal   (Followers: 5)
Tungsten     Hybrid Journal  
Universal Journal of Materials Science     Open Access   (Followers: 3)
Welding in the World     Hybrid Journal   (Followers: 8)
Welding International     Hybrid Journal   (Followers: 11)
Вісник Приазовського Державного Технічного Університету. Серія: Технічні науки     Open Access  
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Journal Cover
Powder Metallurgy and Metal Ceramics
Journal Prestige (SJR): 0.221
Number of Followers: 7  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1573-9066 - ISSN (Online) 1068-1302
Published by Springer-Verlag Homepage  [2656 journals]
  • Composite Ceramics for Thermal Barrier Coatings Produced From ZrO 2 Doped
           with Yttrium-Subgroup Rare-Earth Metal Oxides
    • Abstract: The use of compositionally complex ZrO2-based ceramics doped with a mixture of yttrium-subgroup rare-earth metal (REM) oxides for the deposition of thermal barrier coatings (TBCs) was studied. For research, a heavy concentrate (HC) of yttrium-subgroup REM oxides, consisting of (wt.%) 13.3 Y2O3, 1.22 Tb4O7, 33.2 Dy2O3, 8.9 Ho2O3, 21.8 Er2O3, 1.86 Tm2O3, 12.5 Yb2O3, 0.57 Lu2O3, and 6.65 other oxides (including 3.2 Al2O3), and Y2O3 and M-ZrO2 powders were chosen. The targets for depositing electron-beam ceramic TBC layers—both standard and compositionally complex ones—were made of ceramic mixtures including (wt.%) M-ZrO2–7 Y2O3 and 90 M-ZrO2–10 HC. The properties of the compositionally complex and standard yttria-stabilized ZrO2-based ceramic layers in electron-beam TBCs applied in one process cycle were compared. Two-layer metal/ceramic TBCs were deposited onto model blades by directional crystallization from the ZhS-26VI alloy employing an UE-174 industrial electron-beam installation (ELTECHMACH, Vinnytsia). The ceramic M-ZrO2–7 Y2O3 topcoat was denoted as YSZ and 90 M-ZrO2–10 HC as HCSZ. The MZP-6 alloy (nickel–chromium–aluminum–yttrium) was used to form an inner heat-resistant bond coat. This resulted in rough dense glassy coatings differing by color: light-gray YSZ and dark-gray HCSZ. The coatings were 90–95 μm thick on the blade back side and 90 μm thick on the pressure side. Both coatings included the F-ZrO2 phase. Feather-like microstructures emerged in the coatings. The YSZ topcoat contained two types of dense structures, represented by columns and branched formations, and the HCSZ layer was of irregular microstructure with wide feather-like formations growth together. The laminar microstructure of the ceramic topcoat was due to the process features peculiar to electron-beam deposition. The YSZ topcoat had the following microhardness: 3884 MPa on the back side and 6052 MPa on the pressure side. The HCSZ topcoat had much lower microhardness: 1381 MPa on the back side and 1679 MPa on the pressure side. The compositionally complex coating withstood 161 thermal cycles and the standard coating 138 thermal cycles. Previous studies showed that ZrO2 stabilization with concentrates of yttrium-subgroup REM oxides was promising for the microstructural design of TBC ceramic topcoats.
      PubDate: 2021-05-10
  • Temperature–Composition Dependence of Thermodynamic Mixing Functions of
           Co–Cr–Cu–Fe–Ni Melts
    • Abstract: In the framework of the CALPHAD method, a thermodynamic database was developed for calculating the thermodynamic properties of liquid alloys in the Co–Cr–Cu–Fe–Ni system and its quaternary subsystems. The thermodynamic mixing functions of the melts were calculated at 1873 and 1500 K. The calculated excess integral mixing functions showed positive values in a major part of the composition space of the four-component systems with copper and the Co–Cr–Cu–Fe–Ni system. The ideal contribution to the Gibbs energy of mixing for four- and five-component melts of the Co–Cr–Cu–Fe–Ni system was predominant. The excess Gibbs energy of mixing for equiatomic liquid alloys of the four-component systems with copper and the Co–Cr–Cu–Fe–Ni system was lower in magnitude than the ideal component of the Gibbs mixing energy. With decreasing temperature, the positive deviations from the ideal behavior of the excess Gibbs mixing energy increased and the magnitude of the ideal Gibbs mixing energy decreased, resulting in lower thermodynamic stability of the liquid phase. The calculated separation temperatures for four- and five-component equiatomic Co–Cr–Cu–Fe–Ni melts varied in the 1370–1770 K range. The highest liquid-phase separation temperatures were observed in the melts containing both copper and chromium.
      PubDate: 2021-05-01
  • The Formation and Elastic Behavior of TiNi Intermetallic Sintered From a
           TiH 2 –Ni Powder Mixture
    • Abstract: The phase formation and consolidation processes in TiH2–Ni powder mixtures resulting in TiNi intermetallic were studied. The use of titanium hydride as a precursor in optimal sintering conditions (900–1000°C) allowed a material with optimum porosity to be produced and a liquid phase to be avoided during sintering. The phase formation processes were found to occur rapidly in the sintering of TiH2–Ni mixtures. At sintering temperatures of 900–1000°C, 70–82% TiNi formed. Intermetallic Ti2Ni compound was an additional phase that emerged in the material in all sintering conditions. The stability of this phase was attributed to its affinity for oxygen and thus formation of stable complex oxides. The superfine mixture and highly active titanium resulting from the decomposition of titanium hydride accelerated the oxidation process. Moreover, the interaction with oxygen began sooner than with nickel. The samples produced from the finest mixture were less homogeneous than the samples produced from a coarser mixture. The high-speed interaction between titanium and nickel and rapid oxygen absorption were due to the hydride powder with significantly finer particles. In these sintering conditions, the material had 12–15% porosity and was thus optimum for medical applications. Studies of the mechanical behavior of TiNi alloys revealed an abnormally low elastic modulus of 40 GPa. Experiments on cyclic loading–unloading showed that the initial elastic strain was 1.1% and reversible transformation strain 0.7%. When the strain reached 4%, the elastic modulus decreased to E ~ 32.7 GPa, the total elastic strain increased to εel ~ 2.6%, and damping capability Q–1 became equal to 0.036. The mechanical characteristics of the materials were close to those of human bones. The experimental results demonstrate that the sintered TiN materials exhibit the structure and mechanical properties that make them promising for the design of human bone implants.
      PubDate: 2021-04-30
  • Effects of Compacting Pressure and Sintering Temperature on the Properties
           of Highly Porous Pure Aluminum Produced with Boric Acid (H 3 BO 3 )
    • Abstract: In this study, highly porous pure aluminum material with cellular structure was fabricated via powder metallurgy route using a space holding technique with the addition of boric acid powders as pore-forming agents. Boron products, namely, the boric acid, were used as novel pore-forming agents. Aluminum powders with high porosity of ~50% were successfully produced. The experiments were focused on investigating the effects of such parameters as compaction pressure and sintering temperature on the final properties of fabricated samples by determining their optimum values. Quasistatic compressive behaviors of the obtained highly porous materials were examined at a strain rate of 10–3 sec–1. The results show that the most suitable compressive properties of the highly porous states were obtained for the samples cold-pressed under 630 MPa and sintered at 620°C for 3 hours. According to the stress-strain behavior of the high-porous states, there is a plateau region with nearly constant flow stress and a large strain of about 70%. The densities of these high porous states were approximately 1.0 g/cm3, and the mean cell sizes amounted to about 0.6 mm. Using boric acid (H3BO3) powders differs from conventional processes in terms of superior comprehensive mechanical properties with static compressive strength and energy absorption of 18 MPa, and 12 MJ/m3, respectively.
      PubDate: 2021-04-30
  • The Co–Ni–Zr Phase Diagram in the Zr–ZrCo–ZrNi Region II. Liquidus
           Surface of the Phase Diagram. Interaction of Alloys with Hydrogen
    • Abstract: The results of microstructural, X-ray diffraction, differential thermal, and electron microprobe analyses of Zr–ZrCo–ZrNi cast alloys were used to first construct the liquidus surface of the Zr–ZrCo–ZrNi system on the composition triangle. The liquidus surface was found to consist of four primary crystallization surfaces of the phases: a solid solution of β-Zr and phases based on ZrCo (δ) and ZrNi (δ2) compounds and a θ phase (continuous solid solutions between Zr2Co and Zr2Ni isostructural compounds of AlCu2 type). In crystallization of the alloys, an invariant four-phase transition equilibrium with participation of the liquid phase, L + δ ↔ δ2 + θ, was observed at 1025°C. The constitution of the quasibinary sections of the ZrCo–ZrNi and Zr2Co–Zr2Ni systems, showing a decrease in the solidus and liquidus temperatures of the alloys with increasing nickel content, determined the type of invariant equilibrium. The study of cast alloys confirmed that the phase based on Zr3Co (η) compound formed by peritectoid reaction. A scheme of reactions occurring in Zr–ZrCo–ZrNi alloys in the temperature range from crystallization to solid-state transformations associated with the peritectoid formation of the η -phase and with the martensitic transformation of β ↔ α zirconium was developed. Two vertical sections were constructed using data on phase equilibria in the Zr–Co and Zr–Ni boundary binary systems and data on equilibria on the solidus surface and at 900 and 800°C in the Zr–ZrCo–ZrNi ternary system. Data on the interaction of individual alloys in the system with hydrogen were obtained. Significant rates of absorption and release of hydrogen from the hydrides were observed above room temperature.
      PubDate: 2021-04-29
  • Wear-Resistant TiN–20 wt.% Si 3 N 4 and TiN–20 wt.% TiB 2 Composites
           Produced by Microwave Sintering
    • Abstract: Comprehensive research on microwave sintering of the TiN–20 wt.% TiB2 and TiN–20 wt.% Si3N4 composites was conducted. At a constant microwave power of 900 W, the TiN–20 wt.% TiB2 composite could be effectively consolidated to a residual porosity of 9% at 1370°C and the TiN–20 wt.% Si3N4 composite to a residual porosity of 6% at 1407°C. A comparative analysis of the composites consolidated by conventional sintering in a resistance furnace at 50 °C/min to 1550°C revealed that they had residual porosity greater than 25%. The microwave-sintered samples showed dense areas of predominantly spherical shape (D ~ 5 μm) formed by titanium nitride and titanium diboride phases. This zonal segregation of dense areas to form TiN and TiB2 spherical agglomerates was due to heterogeneous distribution of the electromagnetic field throughout the multimode microwave oven, leading to locally overheated areas within the materials being processed. The structural features of the TiN–20 wt.% TiB2 and TiN–20 wt.% Si3N4 composites were found to influence their mechanical and tribological properties. The measured hardness of the TiN–20 wt.% TiB2 composite was 19.5 ± 1.1 GPa and that of the TiN–20 wt.% Si3N4 composite was 19.8 ± ± 0.8 GPa. Wear resistance tests of the composites in friction against the VK6 hardmetal showed quite high tribological properties: linear wear rates of 12.5 μm/km (TiN–20 wt.% Si3N4) and 11.3 μm/km (TiN–20 wt.% TiB2) and friction coefficients of 0.43 and 0.26, respectively. A comparative analysis of the TiN–20 wt.% TiB2 and TiN–20 wt.% Si3N4 composites consolidated by microwave and conventional sintering allowed the conclusion that a uniform fine-grained structure, which would enhance the mechanical and tribological properties, could be produced by increasing the microwave sintering rate in the 600–1500°C range to 50 °C/min and above and using hybrid microwave heating.
      PubDate: 2021-04-29
  • Fracture Features of Low-Alloy Steel Produced by Metal Injection Molding
    • Abstract: In the manufacture of sintered steels by metal injection molding (MIM), typical microstructural defects, such as pores and pore agglomerates, phase structure heterogeneities, and boundaries between different phases, are hard to avoid. Such heterogeneities cause crack origination, growth, and propagation when sintered materials are subjected to mechanical loads. The crack propagation path and fracture resistance are associated with the complex heterogeneous structure including ferrites, cementites, martensites, pores, and weak interfaces. With increasing sintering times, metal grains grow rapidly, leading to brittle fracture of the samples. Subsequent heat treatment substantially decreases the grain size and changes brittle fracture to ductile one. Multicycle sintering of the Catamold 8740 low-alloy steel greatly increases the impact strength of V-notched samples (from 7.55 to 13.95 J/cm2). Greater density of the samples and fewer stress concentrators favorably influence the material’s capability to withstand impact loads. Thus when density of the billets following six sintering cycles increases by 2.5%, their impact strength becomes 1.8 times higher. With a greater number of sintering cycles, the ductile dimples become significantly larger, while the increase in shock impact and density of the sintered material gradually slows down. The grain size substantially increases (in turn, suppressing pore healing) and density of the samples becomes greater over the total sintering time. X-ray diffraction and spectral analysis revealed additional phases after sintering and heat treatment. Additional fine-crystalline carbide and oxide phases become more distinguished with further increase in the sintering temperature and heat treatment. Brittle inclusions, along with residual porosity, present in sintered steel decrease the dynamic properties of the material.
      PubDate: 2021-04-29
  • Synthesis of High-Entropy AlNiCoFeCrTi Coating by Cold Spraying
    • Abstract: The cold spraying (CS) process was applied to deposit coatings using the AlCoNiFeCrTi high-entropy alloy (HEA) powder. The HEA powder was produced by short-time mechanical alloying (MA) of an equiatomic mixture in a planetary-ball mill followed by annealing at 1200°C and grinding of the resultant agglomerates. X-ray diffraction and microstructural analyses were employed to study the phase and structural transformations at different stages of producing the AlCoNiFeCrTi alloy powder and after it was sprayed onto a steel substrate. When the powder mixture was subjected to the MA process, a metastable nanostructured bcc solid solution formed. Annealing changed the phase composition of the alloy to an ordered bcc solid solution (B2 phase), intermetallic σ-phase (FeCr), and titanium carbide TiC. Grinding in a planetary-ball mill for 1 h turned the ordered B2 phase into a disordered nanostructured bcc solid solution. The titanium carbide and σ phase remained in the alloy, but particles of the σ phase significantly refined and partially dissolved in the bcc solid solution. Following deposition, the phase composition and nanostructured state of the starting alloy powder remained unchanged and the cold-sprayed coating consisted of a bcc solid solution, an intermetallic σ phase, and TiC carbide. The average coating thickness was 405 μm and Vickers microhardness HV was 10.0 ± 0.3 GPa. The high hardness of the coating was due to hardening effects: solid-solution and nanostructured hardening, hardening by inclusions of intermetallic and carbide phases, and strain hardening under severe plastic deformation in deposition at supersonic speeds (~105–107 sec–1) at low temperatures. The HEA coating showed good adhesion to the substrate and low porosity (<1%).
      PubDate: 2021-04-29
  • Microdistortions, Hardness, and Young’s Modulus of Multicomponent
           Bcc Solid Solutions
    • Abstract: The phase composition, type II microstresses, and coherent scattering domains (CSDs) of multicomponent (medium- and high-entropy) bcc solid solutions with an average electron concentration, Csd, ranging from 4.6 to 5.47 e/a were studied. The effect of these characteristics on the hardness and Young’s modulus was analyzed. The alloys were melted in a MIFI-9 vacuum arc furnace using components with a purity of at least 99.5 wt.%; the ingots were remelted six times. The hardness and Young’s modulus of the alloys were determined from nanoindentation curves plotted with a Micron Gamma unit under a load from 0.98 to 2.94 N using a Berkovich diamond pyramid under automated loading and unloading. A relatively small change in the quantitative chemical composition of the samples led to a noticeable change in the lattice parameter, type II microstresses, CSDs, microhardness, and Young’s modulus. The greatest possible type II microstresses and minimum CSD sizes were observed for the alloys characterized by high average mismatch between the atomic sizes of their constituent elements. Increase in the electron concentration in the alloys led to higher hardness and Young’s modulus and lower lattice parameter. Increase in the type II microstresses was also accompanied by higher hardness and Young’s modulus. The microhardness H of alloys significantly exceeded that calculated with the mixture rule, Hmix, and was determined by solid-solution hardening (∆H = H – Hmix ranging between 2.9 and 6.4 GPa). Type II microstresses precisely calculated from the X-ray line width can be used for measuring the distortion of the solidsolution lattice and assessing solid-solution hardening. The relationship between the magnitude of solid-solution hardening, Young’s modulus, and lattice microdistortions (type II microstresses) was proposed.
      PubDate: 2021-04-28
  • Effect of Reinforcement with Micro- and Ultradispersed Diamond Powders on
           the Properties of Diamond Tubular Drills During the Processing of Some
           Non-Metallic Materials
    • Abstract: The study presents the results of comparative laboratory tests of diamond tubular drills when drilling window glass, granite, and abrasive stones based on silicon carbide SiC. The tests were carried out in cold running water. Tin bronze containing micro- and ultradispersed diamond powders of ASM 40/28, ASM 10/7 (MDP), ASM 1/0 (UDDP) grades, and molybdenum powder were used as a matrix of the tool. Furthermore, the dependence of the hardness of specially prepared matrix samples on their composition was examined. With an increase in the ASM 1/0 concentration up to 5 wt.% in the reinforcement, the hardness of the matrix samples increased by one-third and reached a maximum of ~96.5 HRB. A further increase in the ASM 1/0 concentration led to a slight decrease in the hardness of the samples. The use of larger diamond powders required a higher concentration, providing high values of hardness. By adding ASM 10/7 in an amount of 10 wt.% and ASM 40/28 in the amount of 40–60 wt.% we managed to increase the hardness of the matrix to the same maximum. The introduction of a reinforcement in a bonding matrix of diamond tubular drills in amount ensuring its maximum hardness has significantly increased the efficiency of their operation. Thus, the wear of drills after glass processing decreased by 2–6 times, and the drilling speed increased by 3–4 times. Drill wear after granite processing has decreased by 50–84 times, and the drilling speed has increased 2.7–6 times, correspondingly. Finally, after processing of an abrasive stone based on silicon carbide SiC, the wear of diamond tubular drills decreased by 1.4– 2.9 times, and the drilling speed increased by 1.5–2.5 times. The effect of additives in the reinforcement of the tool depended on the choice of the diamond powder grade and their concentration. The best option was the introduction of ASM 1/0 (UDDP) powder in an amount of 5– 9 wt.%. The introduction of ASM 10/7, and especially ASM 40/28 (MDP), into the reinforcement required, firstly, their higher concentration (10–40 wt.%), and secondly, was not effective enough since the wear indicators of diamond tools were higher, and the drilling speed was lower.
      PubDate: 2021-04-28
  • Sintered Aluminum–Graphene Nano-Bio Composite Materials for the
           Medical Application
    • Abstract: It is known that graphene is stronger than steel. It is characterized by extremely high values of the Young's modulus (up to 1 TPa), strength (~125 GPa) and thermal conductivity (~5000 W/(m · K)). Therefore, in this work it is used to obtain nano-bio composite materials aluminum–graphene using powder metallurgy methods, in particular high-energy ball grinding followed by vacuum sintering. Sintered composite materials were evaluated using modern methods of microstructure analysis, such as scanning electron microscopy with field emission (FE-SEM), energy dispersion spectroscopy (EDS), transmission electron microscopy (TEM) and Raman spectroscopy for qualitative and quantitative analysis of aluminum characteristics. According to the results of research, a homogeneous distribution of components is observed in the structure of the material over the given scan areas. The relative density of the composite after sintering is ≈97.5%. Data on the electrical conductivity of aluminum-graphene nano-structured bio-composite materials provide grounds for their use in bone engineering.
      PubDate: 2021-04-28
  • Oxidation Behavior of Ta–W–Ti–Al Multialloys Prepared by
           Spark Plasma Sintering
    • Abstract: In this study, Ta–W–Ti–Al multialloys were prepared by spark plasma sintering (SPS) as a new powder metallurgy technology based on discharge activation and thermoplastic deformation process. The oxidation behavior of the as-obtained sintered alloys were investigated under 1000 and 1200°C in air atmosphere. Microstructures and phase compositions of alloys and oxides were analyzed using various analytical methods, such as X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), and backscatter electron microscopy (BSE). The sintered samples possessed relative densities reaching up to 98% with achievable densification. The densities of all specimens with high Ti contents exceeded 100%, suggesting the great impact of Ti addition on liquid-phase precipitation. Intermetallic compounds were formed in Ta–W–Al alloys, and samples with high Ti contents displayed grain boundary phases rich in titanium and oxygen. The addition of Ti and Al effectively improved the oxidation resistance of the resulting alloys. A protective alumina layer was formed after oxidation at 1000°C that made oxidation kinetics of the alloys obeying pseudo-parabolic laws. At the oxidation temperature of 1200°C, Al2O3 reacted with Ta2O5 to form the AlTaO4 alloy with reduced protective effect. The mass gain in the alloys after oxidation at 1200°C for 4 h was about 7 times higher compared to processing at 1000°C.
      PubDate: 2021-04-28
  • Iron–Paraffin Composite Material for 3D Printing by Fused Deposition
           Modeling Method
    • Abstract: Fe-powder and paraffin-based or similar systems are widely used for low-temperature injection molding. The main attention of research efforts on such compositions is focused on the study of their rheology. At the same time, such materials can be adapted for 3D printing by layer-by-layer surfacing, requiring only necessary rods or filaments with a sufficient level of mechanical properties so as not to break during printing. Hence, this paper examines the influence of paraffin content on the compressive strength of samples made of carbonyl iron powder and paraffin in the ratio: 50/50, 60/40, 70/30, and 80/20 vol.%. Computer calculations of critical deformation, elasticity modulus, and compressive strength of such composites have been performed. According to the examination and calculation results, the modulus of elasticity varies from 1358 to 113 MPa with a higher paraffin content, the critical deformation ranges between 0.257 and 3.310, and the compressive strength is between 0.339 and 0.761 MPa. Iron powder was mixed with paraffin in a planetary mill for 3 min with a subsequent sieving of the mixture. Afterward, pressed cylindrical samples with a volume of ~1 cm3 and a height of ~10 mm were used to determine the density and compressive strength. It was found that the density of the samples after pressing is 1.3 times lower than the calculated by the additivity formula at a binder content of 20 vol.%. Only when the binder content increases to 50 vol.%, the actual density approaches the calculated values, that is, the relative porosity varies from 0.212 to 0. With an increase in paraffin content from 20 to 50 vol.% the strength of the samples increases along the concave curve from 3 to 11 MPa. The dependences of the calculated and experimentally obtained compressive strength are similar, indicating the adequacy of the established models. However, significant variation in values is due to the difference between the properties of paraffin under study and that used for testing. Samples of rods with 40 and 60 vol.% Fe was extruded and tested by 3D printing. The obtained experimental data can be used in the creation of other similar working materials for 3D printing in the layer-by-layer surfacing.
      PubDate: 2021-04-28
  • Effect of TiB 2 on the Phase Composition, Microstructure, and Tribological
           Properties of AlCoCrFeNi/TiB 2 Composites
    • Abstract: High entropy alloys (HEAs) attract more and more attention due to their simple structure, high strength and hardness, good ductility, and excellent softening, oxidation, corrosion, and wear resistance properties. Among the known HEA systems, the AlCoCrFeNi alloy exhibits complicated microstructure and excellent mechanical properties. In this study, the AlCoCrFeNi/TiB2 composites were prepared via power metallurgy route in combination with spark plasma sintering (SPS) technology. At first, the AlCoCrFeNi HEA powders were prepared by gas-atomization technology under Ar atmosphere with the high purity of raw elemental materials. The commercial TiB2 powders with average particle size of about 2 μm were used as the reinforcing agent to prepare the AlCoCrFeNi/TiB2 composites. The effect of TiB2 content on the phase, microstructure, and tribological properties of the synthesized AlCoCrFeNi/TiB2 composites were investigated by XRD, SEM, and EPMA, whereas also through friction and wear tests. The results show that phase transformation occurs with σ phase formation after sintering. The TiB2 particles tend to agglomerate and grow up with increased TiB2 content. The effect of TiB2 on the tribological behavior of the composites was studied through measuring the coefficient of friction (COF) and wear rate (W). The resulting values of COF and W show that the wear resistance of AlCoCrFeNi/TiB2 composites is improved with increasing the TiB2 content.
      PubDate: 2021-03-11
  • Modeling of Multimodulus Elastic Behavior of Damaged Powder Materials
           Using Computational Micromechanics
    • Abstract: The work aimed to improve the fundamental acoustic defectoscopy principles of green compacts and weakly sintered materials. A theoretical method for determining the elastic properties of powder porous materials with distributed microdefects has been proposed. The nonlinear elastic multimodulus (different stiffness in tension and compression) behavior of this material has been described by micromechanical averaging on a representative cell. According to the mechanics of composites, the cell geometry represents the structure of a heterogeneous material, and the boundary conditions on a representative cell enable relating the stress–strain state at the macro- and meso-level. The averaging was carried out by computer simulation using the finite element method with an adaptive mesh, which automatically condensed in the places of the large gradient stress–strain. The structure of the representative cell corresponds to a powder material with ‘imperfect’, i.e., partially stratified, interparticle contacts. In the proposed model, the rheological response of a porous, damaged material is specified by three elastic moduli. The structure of such a material is described by two internal state parameters, namely, the porosity and the degree of interparticle contacts delamination. That is, the elastic moduli are functions of porosity and damage. Accordingly, several values of elastic moduli were calculated for a discrete density and damage range. The advantage of this approach is focused precisely on the powder materials rather than on any damaged material, in general, which allows considering the real structure of the damaged material using the mechanics of microheterogeneous materials. The developed structure-sensitive elasticity model enabled establishing the relationship between the defectiveness of a porous sample and the resonant frequency of its free vibrations.
      PubDate: 2021-03-02
      DOI: 10.1007/s11106-021-00192-7
  • Information on the Annual Report of the Ukrainian Commission on Phase
           Diagrams and Thermodynamics
    • Abstract: The Alloy Phase Diagram International Commission (APDIC) promotes the effective dissemination of data on phase diagrams and thermodynamics of phases in accordance with the required quality standards and furthers the application of phase diagrams in research and industry. The annual report of the Ukrainian Commission on Phase Diagrams and Thermodynamics, which is a member of APDIC as one of the national participants, presents information on the findings of Ukrainian scientists in this field in 2017–2019. Information on the research findings is presented in a table, collecting data on the systems studied and results obtained and listing references to the published papers.
      PubDate: 2021-03-01
      DOI: 10.1007/s11106-021-00182-9
  • Thermodynamic Properties of Tungsten Disulfide from First Principles in
           Quasi-Harmonic Approximation
    • Abstract: The standard values (T = 298.15 K) of thermodynamic properties of hexagonal tungsten disulfide 2H-WS2 were calculated from first principles using density functional theory and quasi-harmonic approximation with finite displacements in supercells. Local density approximation was chosen as the exchange-correlation functional and the calculation was performed without Van der Waals corrections. The calculated data are in good agreement, except for the enthalpy of formation, with reliable experimental results, eliminating the discrepancies between the experimental results from different sources and increasing the overall reliability of thermodynamic data for tungsten disulfide. Additionally, the data agreement suggests that greater attention should be paid to experimental studies of the phonon spectrum of 2H-WS2, particularly in the Γ → K region of the low-energy dispersion, where the deviations between the calculation and inelastic neutron scattering are significant. The values of the heat capacity, entropy, and enthalpy of tungsten disulfide are recommended for incorporation into thermodynamic databases and practical application, and the parameters used to calculate these quantities are recommended as initial parameters in firstprinciples studies of the 2H-WS2 properties related to the vibrational spectrum. The calculated value of ∆fH°(2H-WS2, 298.15 K) = –275 ± 0.5 kJ ∙ mole–1 is about 10% below the median of the existing literature data and about 15% below the experimental result accepted as the most reliable. To improve the result, the calculation requires additional attention, for example, by the application of Van der Waals corrections or hybrid approximations to the exchange-correlation functional.
      PubDate: 2021-03-01
      DOI: 10.1007/s11106-021-00185-6
  • Titanium-Doped Powder Coatings with a TiN Layer on 9KhS Steel and VK8
           Hardmetal Substrates
    • Abstract: The phase and chemical compositions, structure, and properties of titanium/aluminum-doped coatings with a TiN layer on 9KhS steel and VK8 hardmetal substrates were studied. A TiN layer 5.0–5.5 μm thick was applied by the physical vapor deposition method. The alloys were doped with titanium and aluminum in fusible containers in a mixture of powders consisting (wt.%) of 40.0 Ti, 5.0 Al, 5.0 Al2O3, and 5 NH4Cl at 1050°C for 4 h. Multilayer coatings including Al2O3, Fe2Ti4O, TiC, and TiN formed on the 9KhS substrate and Al2O3, TiAlCO2, TiC, and TiN coatings on the hardmetal substrate. The TiN layer completely inhibited the penetration of aluminum into the 9KhS substrate and of aluminum and oxygen into the VK8 hardmetal substrate. The coating on 9KhS steel had no Feα(Al) layer, and the coating on VK8 hardmetal had no area containing aluminum and oxygen. Individual layers in the coatings exhibited high microhardness: 35.6 GPa for the TiC layer on 9KhS steel, 29.0 GPa for the TiC layer on VK8 hardmetal, and 23.4–23.6 GPa for the TiN layer on both substrates. The cross-sectional structure of the coatings was virtually porousless, showing good adhesion between the individual layers and the substrate, being characteristic of diffusionhardened coatings. The wear resistance of the coated 9KhS steel was 6.9 times higher than that of the uncoated steel in dry sliding friction conditions. The coated 9KhS steel showed an extreme dependence of the wear on the sliding velocity. Mechanically fastened indexable hardmetal cutting tools with coatings demonstrated 8.3 times higher resistance than uncoated tools tested by 40Kh13 steel cutting. The coatings developed can substantially increase the performance of 9KhS steel and VK8 hardmetal tools.
      PubDate: 2021-03-01
      DOI: 10.1007/s11106-021-00188-3
  • Effect of Selective Laser Melting Parameters on the Melt Pool Formed by
           Single Tracks of the Heat-Resistant Inconel 718 Nickel Alloy
    • Abstract: The characteristics of single-track melt pools, such as size, shape, and stability, formed by the heatresistant Inconel 718 nickel alloy powder subjected to selective laser melting (SLM) were studied. The objective was to determine the range of optimal SLM parameters to provide a stable track with a depth of two to three layers. Single tracks were built using various combinations of process parameters: laser power from 50 to 400 W with a step of 30 W and scanning speed from 450 to 1000 mm/sec with a step of 50 mm/sec (144 modes in total). An Axiovert 200M MAT light microscope (Carl Zeiss) was employed to examine the cross sections of single tracks and evaluate the geometrical parameters of the melt pools. Features pertaining to the effect of the scanning speed and laser power on single-track depth and width and their ratio were experimentally studied. An unstable track formed at low power (P = 50 W) and low scanning speed (V = 450–500 mm/sec), while no track appeared at all at higher speeds. A stable track formed at power P = 80–200 W at low speeds (V = 500–900 mm/sec) and became unstable and intermittent when speed increased to V = 1000 mm/sec. With higher laser power (P = 230–400 W) and low process speeds, a continuous track formed but had an increased variable width, being indicative of a deviation from the stable track formation conditions. It was first established that the intensity of the scanning speed effect (450–1000 mm/sec) on the single track depth varies by more than 2.5 times depending on the laser power (50–400 W). The process parameters that would ensure the formation of an optimal single track in terms of geometric parameters were determined.
      PubDate: 2021-03-01
      DOI: 10.1007/s11106-021-00183-8
  • Structural and Electrical Properties of Magnesium-Doped CoFe 2 O 4
    • Abstract: In this paper, magnesium-doped CoFe2O4 (Co0.5Mg0.5Fe2O4) compound was synthesized by a solidstate reaction route. The impact of Mg inclusion on the structural parameters of the obtained compound and the subsequent development of thermally-assisted electro-active areas has been systematically examined, as this compound has a fit composition for doping at the site of Co due to its relevantly equal atomic radius. Also, Mg was established as highly ferroelectric and low-weight material. The compound structure and microstructure have been analyzed using the method of scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The dielectric properties were studied over a broad spectrum of frequency and temperature, and quite low dielectric loss was recorded. In the context of impedance and conductivity formalism, frequency-dependent electrical information has been evaluated at varying temperatures. The Nyquist plot represents the effect of grain and grain boundary. Thermally activated non-Debye type relaxation processes were observed in the composites. Jonscher universal power law follows the frequency-dependent AC conductivity at different temperatures. Temperature dependence of AC conductivity at various frequencies indicates a negative temperature coefficient of resistance (NTCR) behavior. Estimating the magnitudes of activation energies in different temperature ranges enables defining the nature of the species involved in the conduction system.
      PubDate: 2021-03-01
      DOI: 10.1007/s11106-021-00190-9
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Heriot-Watt University
Edinburgh, EH14 4AS, UK
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