Powder Metallurgy and Metal Ceramics (v.51, #7-8)

Strain hardening of porous bushings by multiple mandreling: numerical simulation by O. A. Rozenberg; O. V. Mikhailov; M. B. Shtern (379-384).
The surface hardening of porous bushings by multiple mandreling is studied. A deformable liner made of compact metal is used in the process to increase the hydrostatic component of the stress state and to prevent the workpiece from damage. It is established that deformation is local and the deformation zone moves along the length during mandreling. The compaction and hardening regions grow in the radial direction with increase in the number of passes. Alternation of mandreling directions promotes more uniform axial distribution of properties.
Keywords: surface hardening; porosity; plasticity; deformation; finite-element method

Effect of heat treatment on the plasticity of molybdenum-doped iron–copper pseudoalloys by P. Ya. Radchenko; O. I. Get’man; V. V. Panichkina; Yu. N. Podrezov; V. V. Skorokhod (385-390).
The effect of heat treatment on the mechanical properties and microstructure of Fe–30% Cu pseudoalloys doped with 10% Mo is studied. The samples were produced by compacting mechanically alloyed metal powder mixtures and subjecting them to solid-phase sintering (SPS) and liquid-phase sintering (LPS) at 1000 and 1130°C, followed by quenching and tempering. It is shown that doping Fe–Cu pseudoalloys with molybdenum increases the density of the compacts after both SPS and LPS (residual porosity about 1%). The interdiffusion of all the three components promotes the formation of stable heterophase fine-grained microstructure which prevents grain growth and improves the plasticity of the FeCuMo pseudoalloys. Heat treatment increases the strength of FeCuMo and does not affect its high plasticity. The FeCuMo samples produced by SPS and LPS show optimum values of ultimate strength (683–694 MPa and 741–752 MPa), elongation (12.1–12.4% and 8.2–9.4%), and contraction (24.0–25.9% and 12.5–19.7%) after heat treatment.
Keywords: pseudoalloy; iron; copper; molybdenum; heat treatment.

Physicochemical methods are used to study the electronic state of cobalt cations in nanostructures produced by thermal decomposition of salts on the surface and in the bulk of ZSM-5, Al2O3, SiO2, and ERI matrices. It is shown that the electronic state of cobalt is influenced by the type of matrix and cobalt–adsorbed oxygen ratio. It is established that cobalt cations can be immobilized in the tetrahedral and octahedral oxygen environment of the matrix and the oxidation state can change (Co2+ → Co3+) because of the transition from tetrahedral to octahedral coordination.
Keywords: nanostructure; cobalt; electronic state

Rapidly solidified high-temperature aluminum alloys. I. Structure by A. V. Krainikov; O. D. Neikov (399-411).
The paper examines the phase composition of a number of high-temperature aluminum alloys formed in rapid solidification. The main strengthening phases and associated phase transitions in Al–Fe–Ce, Al–Fe–Cr–(TM), Al–Cr–Zr(Mn), and Al–Fe–V(Mo)–Si alloys have been studied. The phase composition of the alloys is shown to be critically dependent on the cooling rate. High-temperature materials are particularly sensitive to the solidification rate since they are doped by nonsoluble elements. Fine quasicrystalline phases, which make a significant contribution to strengthening at low and high temperatures, are present in rapidly solidified materials doped with iron. Besides these phases, Al3TM intermetallics characterized by high thermal stability and low coarsening rate play an important role in modern materials.
Keywords: high-temperature aluminum alloys; rapid solidification; intermetallic phases; strengthening mechanisms; thermal stability; transition-metal doping

Effect of dry friction parameters on the tribosynthesis of secondary structures on composite antifriction iron-based material by A. G. Kostornov; O. I. Fushchich; V. F. Gorban; T. M. Chevychelova; O. D. Kostenko (412-419).
The paper examines the tribological characteristics of a Fe–W–CaF2 composite antifriction material (CAM) in combination with 65G steel during dry friction in air at a high sliding velocity (15 m/sec) and insignificant (0.64–1.28 MPa) pressures. It is established that with twofold increase in pressure (from 0.64 to 1.28 MPa), CAM friction coefficient decreases from 0.25 to 0.20 (by 20%) and wear increases from 0.0158 to 0.03085 mg/km (by 49%) but remains insignificant. The factors acting in the friction process lead to the formation of secondary lubricating films. They prevent mechanical contact between the rubbing surfaces and provide necessary antifriction and operating properties. It is shown that the secondary lubricating films as thin layers with inclusions of solid lubricants differ from the starting material in chemical and phase composition, structural state, and better mechanical characteristics.
Keywords: composite antifriction material; secondary lubricating films; composition; structure; structural state; sliding velocity; pressure; temperature; friction; friction coefficient; wear; synthesis; mechanical characteristics

Wear of multiphase composites in the friction area: mathematical model by V. A. Skachkov; V. I. Ivanov; S. S. Sergienko; T. B. Yanko (420-424).
The wear of multiphase composite materials is modeled as accumulation of microdamage in each component. The probability of damage in the composite components is assessed by solving a statistical boundary-value problem of the micromechanics of structurally inhomogeneous media subject to coupled processes of deformation and microdamage. The accumulation of microdamage is described by random functions whose statistical characteristics for each component are determined experimentally. The approach is validated by comparing the calculated and experimental wear of 15 multiphase composite materials. It is established that the content of fiber reinforcement, thermally expanded graphite, and boron nitride influences the wear of composite materials.
Keywords: multiphase composite; wear; friction; micromechanics; structurally inhomogeneous medium; mathematical model

The effect of porosity on the structure parameters of highly porous cellular and fibrous materials is studied. It is shown that the structure of porous cellular materials is close to the spherical-phase model proposed by Skorokhod and Kondrachuk with coauthors. The structure of sintered fibrous materials shows no noticeable fiber penetration in contact areas, and their structure parameters are better described by models without spherical phase.
Keywords: cellular porous and fibrous materials; models; structure; porosity

Structure and properties of titanium–chromium diboride composites by V. P. Konoval; V. Zh. Shemet; B. Grushko; A. D. Panasyuk; T. V. Mosina; V. I. Subbotin (429-436).
Composites based on binary titanium–chromium diboride are produced by hot pressing. The influence of aluminum nitride additions on the composition, structure, and mechanical and tribotechnical properties of the materials is studied. It is shown that the introduction of up to 10 vol.% AlN into (Ti, Cr)B2 reduces porosity and improves mechanical and tribotechnical properties. The (Ti, Cr)B2–AlN composites were wetted by NiAl alloy and the interaction area was analyzed. The contact angles of wetting are close to zero in this system and terminal solid solutions form in the interaction area. This allowed (Ti, Cr)B2–AlN–NiAl metal ceramics to be obtained. The metal ceramics sintered in vacuum have fine structure consisting of (Ti, Cr)B2 and AlN grains and NiAl alloy.
Keywords: composites; titanium–chromium diboride; aluminum nitride; wetting; hardness; strength; structure

Synthesis of titanium silicon carbide Ti3SiC2 under isothermal sintering by I. I. Ivanova; A. N. Demidik; M. V. Karpets; L. I. Kopylova; N. A. Krylova; A. P. Polyshko; S. A. Firstov (437-446).
The synthesis of Ti3SiC2 in vacuum is studied. The influence of the starting powders, charge composition, and sintering temperature on the phase composition of the material is analyzed. It is established that titanium hydride used instead of metal titanium substantially decreases the onset synthesis temperature and produces almost single-phase material after sintering at 1200–1250°C. However, this Ti3SiC2 does not have adequate density and strength. Practically single-phase Ti3SiC2 with high density and strength is synthesized in the range 1350–1400°C when the silicon content of the charge is higher than its stoichiometric amount by a factor of 1.2–1.25. It is shown that single-phase Ti3SiC2 or material with the required TiC content can be synthesized by variation of silicon content of the charge.
Keywords: sintering; refractory compounds; complex carbides

Effect of the composition and structure of silicon carbide composites on wear mechanisms by A. P. Umanskii; A. G. Dovgal’; A. D. Panasyuk; A. D. Kostenko (447-455).
The tribotechnical characteristics of SiC–Al2O3 and SiC–Al2O3–ZrO2 ceramic composites are studied during dry plane-on-plane friction in a wide range of velocities (2–7 m/sec) and loadings (1– 7 MPa). This testing pattern allows modeling the performance of composites as sealing elements for centrifugal pumps. The influence of 20, 50, and 80 wt.% aluminum oxide in silicon carbide on the wear rate and wear mechanisms is analyzed. It is shown that higher alumina content of the SiC–Al2O3 ceramics changes the wear mechanisms: oxidative–adhesive wear takes place in materials containing 20 wt.% Al2O3 and mechanochemical wear in SiC–80 wt.% Al2O3. The tribotechnical characteristics of SiC–Al2O3–ZrO2 (SIAL-Z) ceramics have been studied. The ratio of aluminum and zirconium oxides in this material is eutectic, which substantially decreases the hot pressing temperature and promotes a fine-grained structure. Oxidative wear takes place in friction of the SIAL-Z ceramics against a steel counterface. This composite has the highest tribotechnical characteristics among the materials of interest.
Keywords: end-face compaction; ceramics; silicon carbide; wear resistance; wear mechanism

Due to their excellent properties such as high specific stiffness, strength/weight ratio, and wear resistance, metal matrix composites (MMCs) with particulate reinforcement and related manufacturing methods have become important research topics in recent years. Magnesium MMCs are materials that are commonly used for fabrication of light-weight functional components. Magnesium MMCs that are reinforced with various fractions of B4C (3, 6, and 9 wt.%) were fabricated by powder metallurgy (PM) technique using a sintering cycle in a vacuum furnace at 590°C for 9 h. A qualitative analysis of X-ray diffraction (XRD) patterns indicated the formation of Al2O3, MgO, and MgB2 phases in the structure of Mg/B4C MMCs. The sintered density of the MMCs decreased with an increase in the amount of B4C addition. The hardness of the MMCs was found to be higher than that of unreinforced Mg. The compressive test results also showed a significant effect of 3 wt.% B4C content on the compressive strength of magnesium MMCs manufactured by the PM technique.
Keywords: magnesium matrix composites; powder metallurgy; B4C; microstructure; mechanical properties

Liquidus surface and melting diagram of the Al–Ti–Pd system in the Al–AlPd–TiPd–Ti region by O. V. Zaikina; V. G. Khoruzha; K. E. Kornienko; T. Ya. Velikanova (463-473).
The solidification of Al–Ti–Pd alloys is studied by light optical and scanning electron microcopy, electron microprobe analysis, X-ray diffraction, and differential thermal analysis in the composition range 0–50 at.% Pd in the Al–AlPd–TiPd–Ti partial system. The liquidus surface projection, melting diagram, and Scheil diagram are constructed for the first time. Eleven regions of primary solidification of ternary compounds, solid solutions based on binary phases, and Ti and Al components are found to exist. The τ3 phase melts congruently while τ1 is formed incongruently.Eleven four-phase invariant equilibria involving a liquid phase exist in the system: two of them are congruent and nine incongruent. The invariant four-phase reactions occur in the temperature range between 630 and 1425–1456°C.
Keywords: liquidus surface; partial system; compound; melting diagram; Scheil diagram

Structural and phase transformations and rate of Ti2Co and TiCo interaction with hydrogen and synthesis of nondestructive nanostructured titanium hydride composites by T. I. Bratanich; O. V. Kucheryavyi; V. V. Skorokhod; L. I. Kopylova; A. V. Kotko; M. O. Krapivka (474-484).
The paper examines the sequence of structural and phase transformations and the rate of Ti2Co and TiCo interaction with hydrogen. Destructive hydrogenation of Ti2Co is used to produce nondestructive nanostructured titanium hydride composites. Thermodynamic analysis has shown that Ti2Co and TiCo destructive hydrogenation is thermodynamically favored in the temperature range 298–973 K. In the temperature range 773–973 K, Ti2Co interacts with hydrogen by destructive hydrogenation reaction, in which hydrogen is dissolved in the intermetallic compound, titanium is selectively hydrogenated to cubic TiH1.9, and titanium-depleted TiCo and TiCo2 intermetallics are successively formed in accordance with the Ti–Co phase diagram. The rate of Ti2Co destructive hydrogenation is proportional to temperature, hydrogen pressure, and surface area of the starting samples. Compound TiCo is hydrogenated to form a solution of hydrogen in Ti1+yCo, intermetallic TiCo2, and a solution of hydrogen in β-titanium. Nondestructive composites with nanostructured components are synthesized by Ti2Co destructive hydrogenation.
Keywords: Ti2Co; TiCo; destructive hydrogenation; nondestructive nanostructured composite

Effect of magnetic treatment on the microstructure and strength of WC–Co detonation-sprayed coatings by V. E. Oliker; Yu. N. Podrezov; I. T. Yarmatov; T. Ya. Gridasova; E. F. Grechishkin; A. G. Gavrilenko (485-490).
The influence of magnetic treatment on fracture of the WC–Co detonation-sprayed coating–St3 steel substrate system is studied in bending tests. It is established that magnetic treatment leads to the redistribution of elements at the coating–substrate interface. It is shown that magnetic treatment improves the mechanical properties of the coating–substrate system: plastic strain of the system increases from 0.15% to 0.35% when coating starts cracking and stresses developed at fracture increase from 700 to 1300 MPa. The improvement of properties is due to better adhesion at the coating–substrate interface resulting from diffusion-controlled redistribution of elements during magnetic treatment.
Keywords: magnetic treatment; detonation-sprayed coatings; fracture toughness; hardmetal

In this study, Al–8%Ti alloy was produced by mechanical alloying. The produced powders were cold pressed at 630 MPa and synthesized at 600°C for 12 and 24 h under argon gas atmosphere. After synthesis processes, the specimens were examined by SEM, XRD, and hardness tests. Wear tests were carried out under dry sliding conditions using a pin-on-disk type machine at a constant load of 30 N and a sliding speed of 1 m/sec. Total sliding distances were selected as 500, 1000, 1500, and 2000 m. The experimental results showed that the hardness and density of Al–%8Ti alloy increased with increasing synthesis time. It was also observed that volume reduction increased with increasing sliding distance and decreased with increasing synthesis time.
Keywords: aluminum alloys; mechanical alloying; wear; microstructure

The paper overviews the origin and development of ceramics from the firing of natural clays to the creation of technical ceramics and advanced structural and functional materials, including nonoxide ceramics with unique components.
Keywords: ceramics; history; ceramic technology; application of ceramics; porcelain; faience; majolica; terracotta; refractories