Powder Metallurgy and Metal Ceramics (v.55, #3-4)

Analysis on Calcination Process of WC–Co Precursor Powder by Qiumin Yang; Jiangao Yang; Jianming Ruan; Jie Wu; Guohua Ni; Tangzhe Ouyang (125-133).
In this paper, calcination of WC–Co precursor powders with different Co contents prepared by solution technique was investigated. Thermal analysis was carried out. The precursor powders after calcination process were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). A mechanism of calcination of the precursor powder was proposed and substantiated by the experimental data. The mechanism was that carbon in Sample C (WC–3 wt.% Co) after calcination was provided only by the pyrolysis of soluble starch, while carbon in Sample A (WC–12 wt.% Co) was provided not only by the pyrolysis of soluble starch but also by the pyrolysis of methyl in acetate cobalt. The main phase after calcination was the mixture of WO3, CoO, and C. Moreover, ultrafine WC–Co composite powder was obtained after fast reduction–carbonization treatment. The morphology of WC–Co powder is hollow spherical granular structure where individual particles are cemented in the form of agglomerated ball and the mean particle size is 177 nm.
Keywords: solution technique ; WC–Co ; thermal decomposition ; calcination ; ultrafine composite

Formation and Propagation of Shock Waves in Highly Porous Materials by M. B. Shtern; E. V. Kartuzov (134-140).
The existence issue of shock waves during dynamic deformation of plastic porous materials is analyzed. The analysis is based on the mechanics of plasticity for porous continuum. The deformation routes typical for both the use of shock resistant materials and dynamic compaction of powders and porous bodies are considered. It is established, that unlike compacts, the deformation of porous bodies can be accompanied by shock waves. For the routes where the changes in volume dominate over the changes in shape, the deformation is always accompanied by the formation of shock waves. Meanwhile, in case of free deposition (and similar routes), shock waves appear only if the starting porosity is high.
Keywords: shock wave ; high porosity materials ; dynamic loading

The effects of mixing method during powder metallurgy (PM) routes on the abrasive wear behavior of Al–Al2O3p composite materials is investigated. For this purpose, starting Al powders with a constant volume fraction of 10% Al2O3p are mixed in a ball-mill, Turbula, and high-energy attritor. Block samples for wear tests are prepared by using the PM process. A pin-on-disc apparatus is used for determining the wear rate. Comparative analyses are based mainly on the wear results, hardness, microstructural evaluation of the samples, and sintering densities. It is established that the samples mixed in the Turbula attritor exhibite the highest density and the lowest hardness. It is revealed that the samples mixed with Turbula have the lowest wear rate, whereas those mixed in the high-energy attritor have the highest wear rate. It is established that the composites demonstrate their optimal characteristics in the samples mixed in the ball-mill attritor.
Keywords: metal-matrix composites ; particle reinforcement ; powder processing ; wear

X-ray diffraction, scanning electron microscopy, and micromechanical tests are employed to study the phase and structural transformations in the Al–Cu–Ni–Fe–Ti and Al–Cu–Ni–Fe–Cr equiatomic powder compositions during mechanical activation and subsequent pressure sintering. The mechanical properties of the high-entropy alloys are examined as well. It is revealed that the AlCuNiFeTi and AlCuNiFeCr nanocrystalline high-entropy alloys produced by mechanical activation consist of supersaturated substitutional solid solutions with bcc crystal structure. It is established that the alloys become three-phase after sintering and consist mainly of bcc solid solutions and an insignificant amount (to 5%) of two fcc solid solutions with different lattice parameters. It is shown that the sintered AlCuNiFeTi and AlCuNiFeCr alloys are characterized by high strength, and their Vickers microhardness reaches 11.2 ± 0.3 GPa and 9.5 ± 0.25 GPa, respectively.
Keywords: high-entropy alloy ; mechanical activation ; pressure sintering ; structure ; phase composition ; mechanical properties

In this study, steels, containing different proportions of C, were produced through powder metallurgy. The microstructure and mechanical properties of the produced powder-metallurgy (PM) steels were examined. The sintered density of PM steels was determined, and their microstructures were identified with optical microscopy, SEM, and EDS analyses. The results indicated that there was a significant increase in strength, but a decrease in elongation with an increase in C content. Considering the advantages of PM method, the results achieved in this study came almost close to rolled steel products.
Keywords: powder metallurgy; steel; microstructure

Structural and Mechanical Properties of Bioactive Glass–Ceramic Composites by O. R. Parkhomei; N. D. Pinchuk; O. E. Sych; T. V. Tomila; G. B. Tovstonog; V. F. Gorban’; Ya. I. Yevych; O. A. Kuda (172-184).
Bioactive glass–ceramic composites based on biogenic hydroxyapatite or synthetic calcium phosphates mixture with addition of sodium borosilicate glass (31.5 wt.%) are prepared using onestage sintering at a temperature of ≤800°C. The comparative analysis of the structure and physical and mechanical properties of the composites produced is carried out. It is established that hydroxyapatite keeps the phase composition (Ca5(PO4)3(OH)) during sintering of the biogenic hydroxyapatite-based composites. During sintering of the composites based on a mixture of synthetic phosphates, a phase transformation and interaction of phosphates with a glass phase occur. This results in the formation of glass ceramics, which contain: calcium silicates (wollastonite CaSiO3) and sodium silicates (Na6Si2O7), sodium-calcium silicates (sodium metasilicate Na2Ca2(SiO3)3 and melilite Na2Ca6(Si2O7)(SiO4)2), sodium borate (Na3BO3), and hydroxyapatite (Ca5(PO4)3(OH). The analysis of porous structure of glass–ceramic composites showed a significant difference in the pore size distribution, depending on the material composition. The difference in the surface and fracture structure for both types of composites is established. It is shown that the mechanical properties of the composites based on biogenic hydroxyapatite are higher compared to those based on synthetic calcium phosphates at the similar total porosity value (32.5–34.5%). This may be due to the phase transformations and interaction of phosphates with glass during sintering and the formation of a complex silica structure. It is established that the strength of the composites produced is comparable to that of the native bone.
Keywords: hydroxyapatite; calcium phosphates; bioactive glass; composites; sintering; structure; porosity; strength

Sintering of Zirconium Diboride and Phase Transformations in the Presence of Cr3C2 by O. N. Grigoriev; V. B. Vinokurov; L. I. Klimenko; N. D. Bega; N. I. Danilenko (185-194).
The kinetics of sintering and phase interactions in the diffusion contact zones of Cr3C2 and ZrB2 are investigated. It is found that using Cr3C2 as a sintering activator for ZrB2 sintering reduces the hot pressing temperature from 2200°C to 1500–1750°C, depending on the Cr3C2 content. The phase formation accompanied with the formation of new high-temperature refractory compounds, such as zirconium carboborides, chromium borides and carboborides, and zirconium-chromium carboborides, rapidly develops at the Cr3C2 and ZrB2 interface within the diffusion zone. An intense diffusion of chromium and carbon into zirconium diboride accompanied with the formation of nonporous states in zirconium diboride (to a depth of 50–100 μm at 1360°C) near diffusion contact zone is observed. It is established that the contact interaction during sintering in the diffusion zone results in the formation of the vanishing eutectic liquid phase, which is consumed to forming new high-refractory compounds (phases based on zirconium carbide and chromium borides).
Keywords: hot pressing in vacuum; compacting kinetics; X-ray phase analysis; contact interaction; diffusion zone; structure and phase formation; X-ray diffraction analysis; vanishing eutectic phase; chemical microinhomogeneity; chromium carbide; zirconium diboride; chromium boride; zirconiumchromium carboboride

Effect of Chromium Diboride Additives in Intermetallic Matrix on the Corrosion Resistance of NiAl–CrB2 Composites in Sea Water by V. A. Lavrenko; A. P. Umanskii; E. N. Polyarus; V. N. Talash; V. A. Shvets; L. M. Kapitanchuk (195-200).
The effect of the amount of chromium diboride additives in the NiAl intermetallic alloy on the corrosion resistance of composites in a 3 % NaCl aqueous solution simulating sea water, using anodic polarization curves, is studied. It is demonstrated that the introduction of more corrosionresistant components (chromium diboride) into the NiAl intermetallic alloy has no significant effect on the durability of such composites in sea water. The basic mechanisms of corrosion in the developed composite materials in corrosive aqueous medium are established.
Keywords: NiAl intermetallic alloy; chromium diboride; composite material; corrosion resistance; sea water; microstructure; Auger analysis; oxide films

Constitution of Alloys and Phase Diagram of the Hf–Ru–Rh System. IV. Liquidus Surface and Melting Diagram of the Partial Ru–HfRu–HfRh–Rh System by L. S. Kriklya; K. E. Kornienko; V. G. Khoruzhaya; V. M. Petyukh; L. A. Duma; A. V. Samelyuk; A. V. Sobolev (201-209).
Using the data obtained in study of the as-cast Hf–Ru–Rh alloys in the range 0–50 at.% Hf and considering the solidus surface constitution, physicochemical analysis techniques are employed to construct for the first time the liquidus surface of the Ru–HfRu–HfRh–Rh partial system onto the composition triangle, the melting diagram, and the reaction scheme reflecting processes during crystallization of the alloys. It is shown that five surfaces of primary crystallization of a continuous series of solid solutions between isostructural (CsCl-type) phases formed by compound HfRu and its high-temperature modification (δ phase), ruthenium and rhodium solid solutions, as well as the ε phase based on compound HfRh3 (AuCu3-type structure) and θ phase based on compound Hf3Rh5 (Hf3Rh5-type structure) are parts of the liquidus surface. Three invariant four-phase processes involving liquid take place at 1900, 1810, and 1720°C.
Keywords: liquidus surface; composition triangle; primary crystallization; solid solution; melting diagram

The Ti–REM–p-element phase diagrams are analyzed in a range up to 40 at.% p-element. Twophase R5X3 + (Ti) and Ti5X3 + (R) phase equilibria are features that distinguish the systems. According to these features, the systems are divided into three types. A system is attributed to a specific type depending on relative thermodynamic stability of R5X3 and Ti5X3 compounds. The factor δ = ∆fH [R5X3]/∆fH [Ti5X3] is proposed to predict the nature of previously unstudied Ti–R–{Si, Ge, Sn, Ga} phase diagrams. If δ < 1, the Ti5X3 phase determines the nature of phase equilibria and the system belongs to type 1. The most characteristic topological feature of systems of this type is the Ti5X3 + (R) two–phase equilibrium. If δ > 1, the R5X3 phase determines the nature of phase equilibria. The system belongs to type 2 and its topological feature is the R5X3 + (Ti) two–phase equilibrium. If δ ≈ 1, the Ti5X3 and R5X3 phases equally determine the nature of phase equilibria, the system belongs to type 3, and its topological feature is (Ti) + τ and (R) + τ equilibria rather than Ti5X3 + (R) and R5X3 + (Ti).
Keywords: phase diagrams ; thermodynamics ; enthalpy of formation

Structural Features and Solid-Solution Hardening of High-Entropy CrMnFeCoNi Alloy by S. A. Firstov; T. G. Rogul’; N. A. Krapivka; S. S. Ponomarev; V. V. Kovylyaev; N. I. Danilenko; N. D. Bega; V. I. Danilenko; S. I. Chugunova (225-235).
The phase composition, microstructure, and mechanical properties of the single-phase CrMnFeCoNi high-entropy alloy with fcc lattice produced by argon-arc vacuum melting are studied. The alloy solid-solution hardening mechanism is analyzed. The abnormally high athermic solid-solution hardening of the alloy is due to variation in the Burgers vector along the dislocation line and a vector component perpendicular to the slip plane. The activation energy of dislocation movement and activation volume are calculated. The activation energy of dislocation movement is close to the activation energy of pure metals with fcc lattices, and the activation volume is significantly lower compared to that of pure metals because picosized distortions grow in the crystal lattice of the multicomponent alloy. The ratio of hardness and yield stress for this alloy is examined.
Keywords: high-entropy alloy; structure; hardness; solid-solution hardening

Effect of Coating Deposition Methods on the Properties of Titanium Aluminide Materials by V. A. Barabash; A. N. Demidik; V. L. Syrovatka; M. S. Yakovleva; I. I. Timofeeva; M. A. Vasil’kovskaya; K. N. Gal’tsov; A. A. Bondarenko; A. E. Terentiev; A. D. Kostenko (236-240).
The behavior of detonation and plasma coatings in conditions of dry friction against titanium alloy OT-4 and stainless steel 07Kh16N6 has been studied. The detonation coatings show significantly better tribological properties than the plasma coatings. This is probably due to the presence of aluminum and titanium nitrides possessing high wear resistance in the detonation coatings. Oxidation of the plasma and detonation coatings at a temperature of 900°C in air has been examined. The detonation and plasma coatings exhibit greater oxidation resistance than uncoated titanium alloy VT-16.
Keywords: coating; titanium aluminum; plasma and detonation coatings; wear resistance

The evolution of knowledge and inventions that contributed to the science of materials has been studied. The development of materials science in the ancient world involved the accumulation of intuitive inventions and the development of crafts. The antiquity established natural philosophy ideas about the nature of matter and divided all existent things into organic and inorganic worlds (Democritus, Epicurus, Aristotle). In the early Middle Ages, alchemy was widespread, with an idea of transmuting elements into gold. Although alchemical ideas were erroneous, they brought some benefits, contributing to the development of scientific experiment. The New Times marked the rapid development of fundamental sciences that promoted theoretical and practical materials science. This paper presents a chronology of the most important inventions and scientific concepts in a tabular form.
Keywords: materials science ; material ; history ; chronology ; natural philosophy ; alchemy ; physics ; chemistry ; mechanics ; metallurgy ; metal science ; properties ; microstructure ; dielectric ; semiconductor ; magnetic material ; ceramics ; composite