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Powder Metallurgy and Metal Ceramics
Journal Prestige (SJR): 0.221  Number of Followers: 7  Hybrid journal (It can contain Open Access articles)ISSN (Print) 1573-9066 - ISSN (Online) 1068-1302 Published by Springer-Verlag  [2468 journals]
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- Production Techniques and Physical and Technological Properties of Nickel
Powders (Review)-
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Abstract: The paper presents a comprehensive analysis of leading trends in nickel powder production techniques. The physical and technological properties of nickel powders are systematized according to chemical composition, average size and morphology of particles and their agglomerates, specific surface area, and apparent density. These data will be useful to potential consumers for the optimal design of functional properties of nickel powder products. The review compares industrial and modern techniques, focusing on their key advantages and disadvantages. The development of new process methods and techniques, such as reduction of nickel oxides with hydrogen in fluidized bed reactors and rotary furnaces, is demonstrated. Various methods for synthesizing nanosized nickel powders for special applications, being at the laboratory research stage, are considered. These methods include deposition and thermal decomposition from solutions using various precursors, synthesis under microwave radiation, laser ablation, plasma chemical synthesis, green synthesis, etc. The properties of powders produced by the reduction of nickel precursors with hydrazine, alkali metal borohydrides, polyols, urotropine, polystyrene, etc. are analyzed. Environmetal and human health concerns related to nickel powder production methods are briefly discussed. Carbonyl, electrolytic, and hydrometallurgical methods allow the production of nickel powders in large quantities but involve high energy consumption and production toxicity. Wet chemistry methods for producing nanosized nickel powders use various toxic chemical reagents, potentially causing environmental issues when implemented industrially. Hydrogen reduction of nickel oxide, as an environmentally friendly method, offers unconditional advantages, including reduced greenhouse gas emissions and zero solvent waste.
PubDate: 2024-08-17
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- Thermal Processes in the Heating of Powder Compacts of Metals and Their
Compositions I. Recrystallization Thermokinetics of Copper Compacts-
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Abstract: The thermal processes of recrystallization in porous copper compacts heated after cold pressing in a steel die were experimentally studied. The recrystallization stages, with temperatures corresponding to data determined with metallographic and other research methods, were identified. Only the first tempering stage was found to occur uniformly throughout the entire volume at a heating temperature of 190°C. Upon further heating, a linear stage ensued, where the temperature remained consistent throughout the entire volume of the material, persisting until the next stage. This was accompanied with energy release, as confirmed by a zero temperature gradient across all regions within the sample. With an increase in temperature to 210–215°C, a thermal surge was observed and visible temperature asynchronization was noted in individual volumes of the sample. However, this was followed by a temperature gradient between individual volumes. At this stage, asynchronized thermal behavior within the sample was observed for the first time, as evidenced by the emergence of thermal waves. Subsequent stages demonstrated nonlinear thermal behavior, evidenced by several competing processes leading to the wave-like transfer of energy accumulated as the copper powders deformed during cold pressing. Like recrystallization processes with first-order reactions in the high-temperature synthesis of intermetallic and other compounds, the emergence of thermal waves was due to several competing processes. Thus, if microplastic deformation processes occurred during recrystallization, then traveling waves could arise in the system, which was actually revealed. This could lead to thermal interference and subsequently to local buildup of thermal energy, potentially causing a sharp increase in temperature in individual areas of the wires deformed during switching and, as a result, their ignition. The temperature surges observed were likely to cause the combustion of insulating materials. Therefore, this can explain the causes of accidents that occur in the operation of complex mechanisms with numerous electrical circuits.
PubDate: 2024-08-14
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- The Influence of Surface Extrusion Densification on the Microstructure and
Mechanical Properties of Iron-Based Powder Metallurgy Gears-
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Abstract: In this study, the surface extrusion densification process is used to improve the surface density, hardness, and mechanical strength of powder metallurgy gears. A mixture of pre-alloyed powders, 0.3 wt.% graphite, and 0.4 wt.% Lube HD lubricant was used as experimental raw materials. These powders were compacted into experimental gears at a pressure of 1,600 MPa and then sintered at 1,120°C for 30 minutes. The sintered gears achieved surface densification by passing through extrusion dies under pressure at a 1 mm/sec speed. The influence of different extrusion amounts (∆W = 0, 0.046, 0.116, 0.186, and 0.246 mm) on the microstructure and mechanical properties of iron-based powder metallurgy gears was investigated (∆W is defined as the reduction in the cross- bar distance between two teeth in the extrusion die plate). The results show that surface densification by extrusion can simultaneously apply normal stress and shear stress, resulting in a reduction of porosity on the gear surface, which in turn forms a densified layer on the surface. The thickness of the densified layer increases with the amount of extrusion. In addition, the surface densification by extrusion improves the surface microhardness and crushing strength of the gears. In particular, the gears with ∆W = 0.246 mm have the highest surface microhardness and fracture toughness. The porous model in DEFORM was used to simulate the surface extrusion densification process. The simulation results showed trends in the relative density distribution consistent with the experimental results, with a higher relative density at the gear surface, followed by a decrease as the distance from the surface increased and the densified region expanded with increasing extrusion amounts. In addition, there was a high degree of correlation between the simulated and experimental results in terms of densification layer thickness.
PubDate: 2024-08-14
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- Mutual Influence of Contact Processes in the Simultaneous Interaction of
Active and Inert Metal Melts with ZrO2 Ceramics-
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Abstract: The processes occurring in the simultaneous contact of ZrO2 ceramics with two metal melts, inert (Cu, Cu–Ga, Ge, Cu–Ge) and active (Cu–Ga–Ti, Cu–Ti), were studied. The experiments were conducted in a high vacuum using thin ZrO2 ceramic plates, with one side in contact with a droplet of active melt and the opposite side with a droplet of inert melt. In the simultaneous interaction of active and inert metal melts with zirconium dioxide, the interface processes showed mutual influence: oxygen-deficient zirconium dioxide (ZrO2–x) was formed through the absorption of oxygen from ZrO2 by the active melt. This contributed to the dissolution of zirconium from the solid oxide in the inert melt, thereby activating it and increasing its adhesion to the substrate. At the same time, the dissolution of zirconium in the inert melt reduced the oxygen deficiency in zirconium dioxide, i.e., restoring its stoichiometry and promoting further absorption of oxygen by the active melt. Thus, with the simultaneous contact of active and inert melts with ZrO2, a larger amount of oxygen dissolves in the active melt, which leads to the saturation of the active melt with oxygen. This results in effects such as the loss of metallic luster and spherical shape of droplets in the active melt, delamination of the active melt, and increase in the thickness of the transition layers at the interface between the active melt and ZrO2. The results are significantly influenced by the amounts of inert and active melts in contact with ZrO2 and by the concentration of the active component (titanium) in the system. The results can be used in the development of methods for brazing and metallization of ceramic materials and techniques for the manufacture and use of refractories and high-temperature electrochemical devices.
PubDate: 2024-08-14
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- Effect of Surface Treatment and BN Content on the Mechanical Properties of
Aluminum Laminates Reinforced with Glass Fiber and Epoxy Resin-
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Abstract: Al laminates are widely used in various applications due to their light weight, corrosion resistance, and good electrical conductivity. In this work, aluminum laminates were reinforced with glass fibers and a boron nitride (BN) epoxy resin. Different concentrations of BN (0, 0.3, 0.6, 0.9, and 1.2 wt.%) were incorporated into the epoxy matrix. The laminates were prepared using a vacuum infusion process (VIP) technique. The addition of BN significantly improved the thermal conductivity of the composites. To further improve the interfacial adhesion between the aluminum alloy sheets and the composite layers, plasma surface treatment was applied to the 6061-T6 aluminum alloy sheets. Plasma surface treatment is a well-known technique that can modify the surface properties of materials, including roughness, wettability, and chemical functionality. By introducing surface roughness and functional groups, plasma treatment can improve adhesion between dissimilar materials. After plasma treatment, the surface morphology and composition of the aluminum alloy sheets were analyzed using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with energy dispersive spectrometry (SEM-EDS). XPS provides information about the chemical composition and bonding state of the surface, while SEM-EDS provides a detailed view of the surface morphology and elemental distribution. Surface roughness and wettability were measured using a surface roughness tester and a contact angle goniometer. The Al/GF/BN/EP laminates were prepared using a thermoforming technique. Mechanical properties including peel, interlaminar shear, tensile, and flexural strength were evaluated. The laminates prepared by plasma surface treatment showed improved mechanical properties with increasing BN concentration up to 0.9 wt.%. This improvement can be attributed to the synergistic mechanism of mechanical and chemical bonding between the metal layer and the composite layer, which is facilitated by the increased surface roughness and the presence of functional groups (C–N and C=N).
PubDate: 2024-08-14
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- Optimization of Detonation Spraying Parameters for (Ti, Cr)C–Ni
Composite Coatings-
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Abstract: The influence of detonation spraying parameters on the porosity and adhesion of (Ti, Cr)C–Ni coatings was studied. These detonation coatings were applied from (Ti, Cr)C-based composite powders containing 18, 25, and 33 wt.% Ni onto a steel substrate. The particle-size distribution of the powders was –63+40 μm. A Dnipro-5M installation was used for detonation spraying. The flow rate of acetylene and oxygen, the air pressure for ejecting detonation products, and the spraying distance were varied in the spraying process. The structure of the coatings was examined by optical microscopy and electron probe microanalysis. The adhesion of the (Ti, Cr)C–Ni coatings was determined by the pin method, and the porosity was measured by the linear Rosival method. In the detonation spraying of (Ti, Cr)C–Ni composite powders, particles of double titanium–chromium carbide refined to 6–7 μm, contributing to the development of a fine and uniform structure of the detonation coatings. It was found that the detonation spraying parameters should be adjusted upward when the nickel content changed from 18 to 33 wt.% in the (Ti, Cr)C–Ni composite powders. The increase in the nickel content from 18 to 33 wt.% resulted in higher adhesive strength and lower porosity of the coatings. In the research, an acceptable level of adhesive strength and porosity could not be reached for the (Ti, Cr)C–18 wt.% Ni detonation coating. The (Ti, Cr)C–33 wt.% Ni detonation coating exhibited the highest adhesive strength (101 MPa) and the lowest porosity (2%) among the studied coatings and is thus promising for further research of its tribological properties.
PubDate: 2024-08-13
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- Thermodynamic Properties of the Glass-Forming Ternary (Fe, Co, Ni,
Cu)–Ti–Zr Liquid Alloys II. Temperature–Concentration Dependence of
Thermodynamic Mixing Functions and Chemical Ordering in Liquid Alloys-
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Abstract: This paper considers the dependence of the thermodynamic properties of glass-forming liquid alloys of the (Fe, Co, Ni, Cu)–Ti–Zr systems on composition and temperature. The associate solution model (ASM) was used as a calculation tool. The results of the calculations correspond to the experimental data on the integral mixing enthalpy, presented in the first part of the work, and reveal the regularities of changes in other thermodynamic functions and the features of interaction between components in these liquid alloys. It was established that the excess thermodynamic mixing functions in each system have negative values, which are determined by pair interactions between Fe, Co, Ni, and Cu as electron acceptors and Ti and Zr as electron donors. The trend of changes in the minimum values of excess thermodynamic mixing functions of the systems shows an increase in their absolute values along the 3d-series from iron to nickel and a significant decrease for copper, which corresponds to a change in the acceptor capacity of metals along the transition series. The temperature dependence of the thermodynamic mixing functions consists in an increase in negative deviations from ideality and an increase in the intensity of interaction between components with a decrease in temperature. The formation of glass-forming liquid alloys from pure metals is accompanied by an increase in the thermodynamic stability of the liquid phase, which is reflected in negative values of the Gibbs mixing energy. In the range of 800–1873 K, the ΔmG function of liquid equiatomic alloys of the systems considered shows values at the level of –20...–35 kJ/mol. Within the framework of ASM, using the total mole fraction of associates as a quantitative estimate of the degree of short-range chemical order, it is shown that liquid alloys of the Me–Ti–Zr system are characterized by significant chemical ordering, which increases with decreasing temperature. Using the empirical rule, the experimentally known compositions of amorphous alloys for the Cu–Ti–Zr and Ni–Ti–Zr systems were interpreted and the composition regions of liquid alloy amorphization were predicted for the Fe–Ti–Zr and Co–Ti–Zr systems.
PubDate: 2024-08-13
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- Synthesis of Lanthanum Pyrochlore–Lanthanum Phosphate Composite Powders
for Thermal Barrier Coating Applications-
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Abstract: Thermal barrier coatings (TBCs) play a critical role in protecting metallic substrates from high-temperature degradation in aerospace and industrial applications. This study was undertaken to synthesize and evaluate a novel lanthanum phosphate zirconate (LaPZ) composite as a potential candidate for TBCs. The LaPZ composite was synthesized by a high-energy ball milling method followed by calcination, which allows precise control over the composition and microstructure. The synthesized LaPZ composite was characterized by various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermal analysis. Lanthanum phosphate was prepared by precipitation method: calcined at 700°C and further calcined at 1,200°C for 2 h. LP-C was used for the preparation of composite powders. It was ball milled at 350 rpm for 8 h, wet milled with distilled water in a high energy planetary mill with zirconia media, and calcined at 1,300°C for 4 h. X-ray diffraction analysis at 1,300°C revealed LaPZ composite powders with a cubic pyrochlore structure of La2Zr2O7 and monoclinic LaPO4. To obtain the pyrochlore structure, LaP and zirconia were taken in two different molar ratios, namely 1 : 1 (LaPZ 1) and 1 : 2 (LaPZ 2). The coefficient of thermal expansion (CTE) of the LaPZ 1 coating was approximately 8.97 · 10–6 K–1. The LAPZ 2 coating exhibited a CTE of 9.15 · 10–6 K–1 when exposed to temperatures ranging from 0 to 1,400°C. Samples maintained stable thermal expansion up to 1,400°C, indicating the suitability of LaPZ for TBC applications.
PubDate: 2024-08-13
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- Thermodynamic Properties of Melts in the Ni–Tb System
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Abstract: The isoperibolic calorimetry method was used to determine the mixing enthalpy of liquid alloys in the Ni–Tb system in the composition range 0 < xNi < 0.6 at 1660 ± 1 K. The minimum mixing enthalpy of melts in this system was –41.8 ± 0.9 kJ/mol at xNi = 0.6. The activities of components and the mole fractions of associates in these melts were calculated according to the ideal associated solution (IAS) model with our and literature values of formation enthalpies for compounds in the Ni–Tb system and with phase diagram data. Two associates were selected for the calculations: TbNi and TbNi5. The activities of the components showed large negative deviations from the ideal solution, with the simplest associate, TbNi, being predominant (xmax = 0.65). The second associate was present in a much smaller proportion (xmax = 0.22). These data correlate with the mixing enthalpies of the melts, formed with significant exothermic effects. To assess the reliability of the formation enthalpies of compounds and melts in the Ni–Tb system, they were compared with those of LnNi5 compounds and liquid alloys in the Ni–Ln system. All were determined with different options of the calorimetry method. Hence, to be compared, they were plotted as a function of the Ln atomic number. Most of the data points aligned with two trend lines, except for the data for compounds in binary Ni–Gd(Dy, Er) systems and melts in binary Ni–Ce (Eu, Yb) systems. Regarding these ΔHmin values, which are more exothermic (Ni–Ce system) and less exothermic (Ni–Eu(Yb) systems) than all others, they may be attributed to the electronic structures of atoms in the components of the melts. The Eu and Yb atoms are known to have half-filled and completely filled 4f orbitals, while the Ce atom contains one electron in the 4f orbital. Therefore, Eu and Yb are divalent and Ce is tetravalent in the nickel alloys. Since nickel is a strong electron acceptor, the energy of its interaction with Ce is greater and that with Eu and Yb is lower compared to other neighboring lanthanides.
PubDate: 2024-08-13
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- Two-Layer Composite Coatings Reinforced with Iron Borides
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Abstract: The furnace infiltration technique was proposed to produce two-layer macroheterogeneous composite coatings. The technique involved consecutive infiltration of hard alloy reinforcement granules with two metallic matrices differing in the melting point. The infiltration resulted in a twolayer composite coating, with the layers being strengthened with the same reinforcement but not having the same matrix compositions. The Fe–12.5% B–0.1% C alloy was used as the reinforcement and the L62 copper-based alloy or hypoeutectic Fe–3.5% B–0.2% C alloy was the matrix. Quantitative metallography, energy-dispersive microanalysis, and microhardness measurements were employed to examine the structurization of interfaces between the boride reinforcement and the molten matrices. Furnace infiltration ensured virtually defect-free structure of the two-layer composite coating, with porosity not exceeding 5 to 7%. This was achieved through the dissolution of reinforcement surface phases in the molten matrices during infiltration without forming brittle intermetallic phases at the interfaces. The intensity of contact interaction processes at the interfaces between iron borides and iron- and copper-based matrices was compared. The mechanical and performance properties of the composite coating layers were studied. The combination of two layers prevented the delamination of the composite coatings under nonuniform distribution of temperatures, stresses, and strains. This determines the prospects of using the proposed technique for surface strengthening of aerospace engineering parts.
PubDate: 2024-08-12
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- Structure and Mechanical Properties of WC-Based Hardmetal with a
High-Entropy NiFeCrWMo Binder-
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Abstract: An equiatomic NiFeCrWMo high-entropy alloy (HEA) produced by mechanical alloying was used as a binder alternative to cobalt for the manufacture of WC-based hardmetals. The WC–10 HEA (wt.%) powder mixture was homogenized in a planetary-ball mill for 2 h and consolidated by electron beam sintering (EBS) for 4 min at a temperature of 1450°C and spark plasma sintering (SPS) for 10 min at a temperature of 1400°C. The relative density of the sintered samples reached 99.4%. The phase composition, microstructure, and mechanical properties of WC–10 HEA hardmetals were studied by X-ray diffraction, scanning electron microscopy, and microindentation. The effect of the NiFeCrWMo HEA binder on the microstructure and mechanical properties of WC–10 HEA hardmetals in comparison with the conventional VK8 hardmetal (WC–8 Co) was determined. The WC–10 HEA hardmetal consolidated by EBS consisted of WC grains, a NiFeCrWMo HEA binder with a bcc structure, and a small amount (3.5%) of complex carbide (Ni, Fe, Cr)xWyCz, whereas the amount of the complex carbide after SPS increased to 47% due to longer sintering and pressure application. No noticeable growth of WC grains was observed during sintering of the WC–10 HEA hardmetal because of the multielement composition of the NiFeCrWMo HEA binder and the formation of complex carbide (Ni, Fe, Cr)xWyCz layers, preventing the growth of WC grains. The hardness HV and fracture toughness KIc of WC–10 HEA hardmetals after EBS were 18.9 GPa and 11.4 MPa · m1/2 and those after SPS were 19.9 GPa and 10.8 MPa · m1/2. The hardmetals with a HEA binder exhibit an excellent combination of hardness and fracture toughness. These values are higher than those for the conventional VK8 hardmetal (WC–8 Co) produced by EBS for 4 min at 1350°C, whose hardness is 16.5 GPa and fracture toughness KIc is 9.5 MPa · m1/2.
PubDate: 2024-06-07
DOI: 10.1007/s11106-024-00417-5
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- Effective Plastic Properties of Porous Materials with an Inverse Opal
Structure-
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Abstract: The paper presents a theoretical evaluation of the mechanical properties of porous materials with an inverse opal structure, which is important for their application in various technological fields. The study focuses on a porous nickel-based material produced by a sequential multistep process that includes the self-assembly of polystyrene spheres, sintering, electrolytic deposition, and subsequent removal of polystyrene to achieve the desired structure. The study covers the process of transition from elastic to irreversible deformation. The objective of this study is to apply the finite element method to model the transition process to reveal the relationship between the structural characteristics of materials, such as porosity and coating thickness, and their mechanical properties. The yield surface was constructed by computational modeling on a representative cell with a number of points in the (p, τ) plane for two cases of opal structure: a highly porous uncoated structure and a structure with an additional solid phase layer. One of the results included approximation of the yield surface with a phenomenological Deshpande–Fleck crushable foam model available in finite element modeling packages. The conclusions show that the effective plastic properties of materials with an inverse opal structure significantly depend on their porosity level and the presence of additional coatings. The yield curve plotted for a porosity of 0.9 is close to the associated plastic flow law, allowing the material’s behavior under loading to be assessed from the uniaxial stress state. However, for a structure with medium porosity and an additional coating layer, the surface becomes significantly unassociated, with a discrepancy of almost 30%. The application of the Deshpande–Fleck model for crushable foam in the approximation of the numerical data from the study demonstrates its relevance in describing the plastic behavior of this structure only at high porosity values.
PubDate: 2024-06-06
DOI: 10.1007/s11106-024-00418-4
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- Evolution of Pore Structure in Compacts Produced from Nickel Carbonyl
Powders during Sintering-
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Abstract: The influence of pore structure evolution in compacts sintered from nickel carbonyl powder with an average particle size of 1.4 μm in the temperature range 200–1000°C on local and bulk shrinkage was analyzed. The pore structure of the samples was characterized by the maximum and average diameters of pore channel constrictions determined by the Barus–Bechhold method. To minimize local (incoherent) shrinkage in the sintering of fine nickel powders, a criterion for pore structure homogeneity in compacts, α ≤ 0.03, was selected. The criterion was determined by the difference between the maximum and average diameters of pore channel constrictions. The influence of pore structure evolution on local and bulk shrinkage during sintering of compacts produced from nickel carbonyl powder with an average particle size of 1.4 and 4 μm was experimentally confirmed. The local shrinkage was due to the three-level structure and wide particle size distribution of the nickel carbonyl powders. A method was proposed to determine the average diameter of particles (agglomerates) in nickel carbonyl powders using the Kozeny equation, establishing a relationship between the particle diameter, the maximum diameter of pore channel constrictions, and the porosity of the compacts, varying from 0.25 to 0.45.
PubDate: 2024-06-04
DOI: 10.1007/s11106-024-00415-7
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- DEM Research on Stress and Force Chains during Warm Compaction of
Intricate Parts-
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Abstract: A Discrete Element Method (DEM) was applied to establish a model that simulates a cross-shaped powder system under hot compaction. The average stress, force chains, principal stress angles, and coordination numbers were recorded and studied. The experimental results show that the stresses in the vertical part of the cross-shaped powder system are higher than in the lateral part, and the highest stress value is always concentrated in the upper zone of the system. This is also consistent with the strength of the force chains in the vertical part being stronger than that in the lateral part. The angle of the principal stress is consistent with the direction of the external load and shows anisotropy and irregular distribution during the compaction process. The vertical section of the cross-shaped powder system tends to be 90°, except for the area close to the lateral section, which tends to be 70°. However, the principal stress angle of the lateral part tends to be 0° during the compaction process. The coordination numbers of the measurement circles have a series of sudden changes and increase with the pressing, the changes of which correspond to the stress distribution.
PubDate: 2024-06-04
DOI: 10.1007/s11106-024-00414-8
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- Study of Geometric Parameters and Mechanical Properties of Metal-Based
Composites-
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Abstract: As the aerospace industry continues to grow, so does the demand for new materials that can withstand high temperatures and corrosive environments. In this paper, materials from the Ti–Al–C system that thrives in the aforementioned environments are studied. The method of measuring the grain size was described according to the relevant standards. The geometrical parameters of titanium carbide and its volume fraction have been determined under the ASTM E112 and ASTM E562 standards, respectively, for two series of specimens that were produced with different parameters and methods. The grain sizes determined are G12 and G12.5 according to ASTM E112. The volume fractions determined for the two series of samples are 20.22 and 17.65%, respectively. Using the above parameters, elastic and shear modulus, and Poisson’s ratio were determined for the specimens tested using RVE modeling. RVE results showed that materials with higher volume fractions and larger average grain size resulted in stiffer materials. Specimens with higher TiC content exhibited higher elastic and shear modules, which were 153.6 and 58.3 GPa, respectively. Poisson’s ratio was the lowest at 0.315. However, the difference was not significant between the specimens, the elasticity and shear modulus, of a specimen with a lower concentration of TiC, are 145 and 55.2 GPa, respectively. Poisson’s ratio was higher and equal to 0.319. Comparing the above properties with the popular aerospace alloy Ti–6Al–4V, both specimens are much stiffer.
PubDate: 2024-06-03
DOI: 10.1007/s11106-024-00419-3
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- Binding Effect of Copper on Physical, Mechanical, and Thermal Properties
of Mg/Ti/Cu Composites-
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Abstract: Metallic reinforcing titanium is added to the magnesium matrix to improve the mechanical properties without losing ductility. Titanium has negligible solid solubility in magnesium below 500°C therefore it does not form a tertiary hard phase with Mg. Therefore, when titanium is added to magnesium, both strength and ductility are improved. However, due to the low solid solubility of Ti in Mg, the bonding between matrix and reinforcement is poor. Therefore, a small amount of metallic reinforcement Cu is added to fabricate Mg/Ti/Cu hybrid composites by powder metallurgy technique to enhance the bonding between Mg and Ti. Cu is selected as a binding agent because it has significant solid solubility with Ti and Mg. In the present work, the effect of Cu on the physical, mechanical, and thermal properties of Mg/Ti/Cu composites has been investigated. The addition of Cu was found to decrease the strength, hardness, and wear rate. On the other hand, the thermal conductivity increased. The strength, wear resistance and thermal stability of the prepared Mg- based hybrid composites are sufficient enough to replace some components of cast iron and aluminum in automotive special seat frames, door panels, brake disks of light-duty vehicles, etc. Thus, the prepared material is recommended for use in automotive and other industries.
PubDate: 2024-06-01
DOI: 10.1007/s11106-024-00420-w
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- Influence of Humidity on the Dielectric Properties of Two-Dimensional
Microsized Molybdenum Disulfide Powders-
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Abstract: Changes in the dielectric properties of two-dimensional (2D) microsized molybdenum disulfide powders in response to ambient air humidity at room temperature were studied (impedance spectroscopy, 1 Hz–20 MHz). The microsized 2H-MoS2 powders were found to absorb significant amounts of moisture (0.43–2.88 wt.%, 3.5 h, relative air humidity of 45–100%). According to impedance spectroscopy data, reversible water intercalation/deintercalation processes led to significant changes in the dielectric properties (total, active, and reactive (capacitive) resistance, capacitance, loss tangent, and real component of relative permittivity) of 2H-MoS2 powders until equilibrium was reached. In equilibrium, the dielectric properties depended on humidity and frequencies. The dielectric properties of microsized 2H-MoS2 powders are dynamic functional characteristics that can be effectively controlled over wide ranges by varying the humidity and frequency levels. It is assumed that changes in the dielectric properties of microsized 2H-MoS2 powders are due to the formation of 2D nanosized MoO3–x/MoO3/H+x(H2O)yMoS2 heterostructures on the surface of the intercalated H+x(H2O)yMoS2 phase particles. These findings can be used to improve nanotechnologies that use aqueous environments, optimize the semiconductor, tribological, and catalytic properties of 2H-MoS2, and develop multifunctional 2D nanomaterials (humidity sensors, sorbents, and photocatalysts for water purification and electro(photo)catalysts for hydrogen production by water electrolysis).
PubDate: 2024-06-01
DOI: 10.1007/s11106-024-00413-9
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- Spark Plasma Sintering of Al2O3 Reinforced Aluminum Alloy Metal Matrix
Composites (Review)-
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Abstract: Aluminum matrix nanocomposites (AMNCs) are a distinct category of advanced materials that incorporate nanoscale reinforcement in a ductile material matrix. Various nanomaterial reinforcements for AMNCs have been reported in the literature, including multi-walled carbon nanotubes (MWCNT), graphene nanoplatelets, silicon carbide, and boron nitride. These classes of materials have been described to exhibit both improvements and reductions in mechanical properties. The interfacial material phases result in low-strength materials. Improvements in mechanical properties are attributed by refined grain size and shape for both the matrix material and the reinforcement agent. These materials demonstrate higher hardness, yield strength, and wear corrosion compared to conventionally prepared aluminum composites. Spark plasma sintering (SPS) is one of the non-conventional sintering methods used to prepare metal matrix composites, resulting in fully dense composite materials. The SPS-produced metal matrix composite can be manufactured rapidly and finds its applications in the automotive, aerospace, and defense industries. This review provides an overview and current status of metal matrix composites regarding matrix and reinforcing materials and the SPS process for producing metal matrix composites.
PubDate: 2024-05-31
DOI: 10.1007/s11106-024-00416-6
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- Wear-Resistant Coatings Produced from TiN–TiB2 and TiN–Si3N4
Composites by Electrospark Deposition and Laser Processing-
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Abstract: The TiN–20% TiB2 and TiN–20% Si3N4 nanocomposites sintered in a microwave field with a frequency of 2.45 GHz were applied to a steel substrate by electrospark deposition in the temperature range 1400–1500°C in a nitrogen atmosphere. In deposition modes with an energy of isolated pulses ranging from 0.2 to 0.75 J, changed surface layers consisting of a coating 50–90 μm thick and a heat-affected zone of increased hardness 40–60 μm thick on the substrate were produced. A part of the samples was subjected to additional surface laser processing to increase the density and homogeneity of the deposited layers. Substantial influence of electrospark mass transfer on the phase composition of the transferred material was established. According to XRD data, the TiN–TiB2 composite, with all its components being present in the coating, was more stable. In the case of the TiN–Si3N4 composite, silicon nitride completely dissociated to form Ti5Si3 and Ti2N compounds. For both compositions, iron, penetrating into the coating from the substrate, was found in the deposited layer. The TiN–TiB2 and TiN–Si3N4 coatings had a hardness of 14–15 GPa and 11–12 GPa, respectively. Comparative tribotechnical tests of the coatings with a spherical VK6 hardmetal counterface in quasistatic and dynamic modes revealed that the electrospark deposition of the TiN–TiB2 composite combined with subsequent laser processing was highly efficient. In tribotechnical tests, the linear wear of this coating was 0.5 μm, corresponding to a twelvefold increase in the wear resistance as compared to that of the TiN–Si3N4 coating for dynamic friction tests. The deposition of the TiN–Si3N4 composite enabled a double increase in the wear resistance of the substrate in dynamic testing mode. In this case, additional laser processing of the coating turned out to be inefficient.
PubDate: 2024-05-31
DOI: 10.1007/s11106-024-00421-9
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- Thermodynamic Properties of the Glass-Forming Ternary (Fe, Co, Ni,
Cu)–Ti–Zr Liquid Alloys I. Mixing Enthalpies of Liquid Alloys-
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Abstract: Data on the mixing enthalpies of liquid alloys in ternary Me–Ti–Zr (Me = Fe, Co, Ni, Cu) systems and boundary binary systems are summarized. The partial mixing enthalpies of titanium and zirconium and the integral mixing enthalpy of liquid Co–Ti–Zr alloys were investigated for the first time by high-temperature calorimetry at 1873 K along the xCo/xTi =3 section at xZr = 0–0.57 and xCo/xZr = 3 section at xTi = 0–0.54. It was shown that the investigated partial and integral functions were characterized by significant negative values. The isotherms of the integral mixing enthalpy of liquid Fe–Ti–Zr alloys at 2173 K and liquid Co–Ti–Zr alloys at 1873 K are described using the Redlich–Kister–Muggianu polynomial. A new description for the liquid Cu–Ti–Zr alloys at 1873 K is also presented. The negative values and composition dependence of the ∆mH function for liquid alloys of each ternary system are determined by the predominant influence of MeTi and MeZr pair interactions, in which iron, cobalt, nickel, and copper are electron acceptors, while titanium and zirconium are donors. In the considered series of the binary Me–Ti and Me–Zr systems and ternary Me–Ti–Zr systems, the absolute values of the integral mixing enthalpy of liquid alloys increase in the transition from the iron systems to the nickel systems and are minimal in the systems with copper.
PubDate: 2024-05-29
DOI: 10.1007/s11106-024-00422-8
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