Powder Metallurgy and Metal Ceramics (v.49, #9-10)

The lanthanides and actinides are placed in the periodic table. It is shown that they can be located without changes in the structure and in the periodic system as a whole taking into account the interatomic donor-acceptor effects in f-elements. The proposed position agrees well with the physical and chemical concepts on which the system is based. It is shown that Am, Pu, and Np can be placed in groups III, IV, and V in accordance with their basic valence states and the capability to form compounds with a valence greater than the group valence. A short-form periodic table is provided in which f-elements are placed in the reverse order of periodicity.
Keywords: periodic table; f-elements; lanthanides; actinides

The Al2O3–HfO2–La2O3 phase diagram. I. Liquidus and solidus surfaces by S. M. Lakiza; Ya. S. Tishchenko; Z. O. Zaitseva; V. P. Red’ko; L. M. Lopato (516-527).
Physicochemical methods are used to study the phase equilibria during crystallization of alloys in the Al2O3–HfO2–La2O3 system for the first time. Liquidus and solidus projections onto the concentration triangle, a melting diagram, and a crystallization scheme are constructed. No new ternary compounds and appreciable ranges of ternary solid solutions are found in the system.
Keywords: ceramics; hafnia; alumina; lanthana; phase diagram; eutectic materials

Microstructural design of ZrO2–Y2O3–CeO2–Al2O3 materials by E. V. Dudnik; A. V. Shevchenko; A. K. Ruban; V. P. Red’ko; L. M. Lopato (528-536).
It is shown that microstructural design of ZrO2–Y2O3–CeO2–Al2O3 ceramics is based on interrelated processes in the synthesis of starting powders and their formation and sintering. Hydrothermal nanocrystalline powders are examined to establish the formation of self-reinforced and multilayer composites with high strength and bioinert implants of femoral heads resistant to ageing processes in the human body. The results serve as a scientific basis for microstructure design of fine-grained ZrO2-based composites in the ZrO2–Y2O3–CeO2–Al2O3 system with high strength and other properties.
Keywords: ZrO2–Y2O3–CeO2–Al2O3 system; nanocrystalline powder; self-reinforced composite; multilayer composite; surgical scalpel; bioimplant

Transparent ceramics based on yttrium subgroup lanthanide, yttrium, and scandium oxides by A. V. Shevchenko; V. A. Dubok; E. V. Dudnik; A. K. Ruban; L. M. Lopato (537-545).
Transparent C-Y2O3–based ceramics characterized by optical transmission in visible and nearinfrared regions and translucent ceramics based on oxides of yttrium subgroup lanthanides are produced. Initial nanocrystalline powders are produced with heterophase mechanochemical treatment in an acid medium with doping cations. The effect from oxides of subgroup IVb (SiO2, PbO) elements, which promote liquid-phase sintering in the production of transparent ceramics, is established.
Keywords: HfO2–ZrO2–Y2O3(Ln2O3) system; nanocrystalline powder; transparent ceramics

Synthesis of cordierite by crystallization from MgO–Al2O3–SiO2 tempered glass by V. M. Pavlikov; E. P. Garmash; V. D. Tkachenko; I. V. Pleskach; B. K. Lupin (546-552).
Physicochemical research is conducted to examine the phase formation under dynamic and static annealing of MgO–Al2O3–SiO2 tempered glass (composition range adjacent to stoichiometric cordierite). Thirty glass compositions are examined in this system and the range is determined over which single-phase ceramic materials with the lowest possible thermal expansion coefficient are synthesized under specific crystallization conditions.
Keywords: synthesis; cordierite; stoichiometry; glass phase; thermal expansion coefficient

Effect of mineral and phase composition of starting mixtures on solid-phase synthesis of cordierite by V. P. Pavlikov; E. P. Garmash; V. O. Yurchenko; O. M. Grigorˈev; V. V. Pavlikov (553-563).
The paper examines the phase transformations and synthesis of cordierite under solid-phase sintering using different natural and synthetic minerals, including binary compounds (mullite, spinel, enstatite) formed in intermediate stages. It is established that the synthesis of cordierite takes two stages: formation of three thermodynamically stable binary oxide compounds such as magnesium–aluminum spinel, mullite, and enstatite and formation of cordierite from a multiphase mixture containing, besides binary compounds, free crystalline α-Al2O3 and SiO2 oxides.
Keywords: minerals; solid-phase synthesis; cordierite; binary compounds; thermal expansion; phase transformations; eutectics

Mechanochemical activation of kaolin, pyrophyllite, and talcum and its effect on the synthesis of cordierite and properties of cordierite ceramics by V. M. Pavlikov; E. P. Garmash; V. A. Yurchenko; I. V. Pleskach; G. S. Oleinik; O. M. Grigor’ev (564-574).
The paper examines the mechanochemical activation of starting minerals (kaolin, pyrophyllite, and talcum) and their effect on the solid-phase synthesis and properties of cordierite. Binary oxide compounds (spinel, mullite, enstatite, forsterite) are synthesized. It is established that binary compounds and crystalline silica should be minimized to decrease the synthesis temperature of cordierite. Processes for synthesis and production of cordierite ceramics with lower thermal expansion coefficient ((1.0–1.2) ⋅ 10–6 °C–1) are developed.
Keywords: natural minerals; mechanochemical activation; pyrophyllite; kaolin; talcum; cordierite; solid-phase sintering; thermal expansion coefficient

New materials and processes for improvement of hip prostheses by V. A. Dubok; V. V. Lashneva (575-580).
Efforts made at the Frantsevich Institute for Problems of Materials Science to improve the functional characteristics and optimize the design of domestic hip prostheses are reviewed. These efforts are focused on new biomaterials, such as tetragonal zirconia bioceramics made of highly pure nanocrystalline powders, nanostructured bioactive ceramic coatings, and new titanium alloys without toxic elements, and new processes such as improved machining of ceramic heads using special diamond nanopowders and advanced software for optimizing the design of hip prostheses and process control.
Keywords: hip prosthesis; structure; ceramic head; zirconia; nanocrystalline powders; nanostructured bioactive coatings

The paper analyzes the Ruff–Wiederhorn hypothesis that several particles participate in one erosion event in a stream of solid particles for plastic materials. The proposed erosion model is based on two kinds of particles, primary and secondary, that differently participate in the erosion process. The primary particles create a crater with a ridge around it due to residual deformation and the secondary particles remove the displaced material. The number of secondary particles in an erosion event is determined by criterial generalization of experimental data. It is shown that the dependence of the erosion rate on the particle speed changes its power from 3 up to 2 at small and large impact speeds, respectively. The erosion rate increases with heating to a certain limit as the number of secondary particles decreases. Too hard particles, which promote high sound speeds, decrease the erosion rate as compared with softer particles because of reduction in contact time.
Keywords: erosion in a stream of solid particles; ductile materials; erosion event; primary and secondary particles; erosion rate; similarity criteria

Pressing and sintering of binary mixtures based on nanosized hydroxyapatite by V. V. Skorokhod; S. M. Solonin; V. A. Dubok; L. L. Kolomiets; T. V. Permyakova; A. V. Shinkaruk (588-593).
The paper examines the pressing, sintering, and structure of binary (hydroxyapatite–pyroceram and hydroxyapatite–tricalcium phosphate) powder mixtures. It is shown that the compactibility of these powder mixtures is an additive function and depends on pure components. The sinterability of the HA–TCP mixture obeys the same law. The HA–pyroceram powder mixture is sintered in the presence of a liquid phase whose amount depends on the particle size of HA, as established experimentally. The use of nanosized powder intensifies diffusion even in solid state due to the great interface area and leads to additional crystallization of the amorphous phase.
Keywords: compactibility and sinterability; hydroxyapatite–tricalcium phosphate; hydroxyapatite–pyroceram; amorphous phase

Sintered manganese steels produced using copper-bearing ferromanganese master alloy by G. A. Baglyuk; L. A. Sosnovskii; V. I. Vol’fman; A. I. Khomenko (594-597).
The paper examines the properties of sintered manganese steels produced with the use of copper-bearing ferromanganese master alloys depending on the master alloy content and sintering temperature. It is shown that increase in the master alloy content promotes higher strength and hardness. The interaction of master alloy particles with the matrix material is accompanied by much more uniform distribution of copper in the grain as compared with manganese, whose inclusions are mainly distributed at the boundaries of iron powder particles.
Keywords: sintered manganese steel; master alloy; iron powder; ferromanganese; sintering

The recombination of Ti3Al from products of destructive hydrogenation (α-TiHx, β-TiHy, TiH1.9(c), TiH2(t), TiAl2, and TiAl3) is studied. It is established that recombined Ti3Al is an ordered alloy with domain structure. The cross-sectional size of domains varies from 70 to 200 nm. The hardness of recombined Ti3Al is 40% higher than that of starting Ti3Al. The materials subjected to destructive hydrogenation and recombination are used for detonation spraying of coatings. The coatings have a small amount of brittle phases and narrow or absent boundaries between individual layers and between the coating and the substrate. The coatings made of hydrogenated powders have twice as strong bonding with the substrate as the coatings made of Ti3Al powder produced by mechanical grinding of ingots.
Keywords: α2-Ti3Al; recombination; detonation-sprayed coating

Phase states of Fe–Mo–C spinning alloys at high temperatures by T. A. Velikanova; M. V. Karpets; P. G. Agraval; M. A. Turchanin (606-615).
Evolution of the phase composition of Fe–Mo–C spinning alloys is investigated in situ with hightemperature x-ray diffraction from room temperature to solidus. The temperature range over which the metastable β-Mn–like phase exists is determined. It is shown that the γ-Fe-based fcc-phase and Mo2C-based solid solution coexist in equilibrium at 1273 K and the γ-phase and η-carbointermetallide of W3Fe3C type coexist with the liquid phase at 1473 K. The vertical section at 11 at.% carbon is plotted.
Keywords: Fe–Mo–C system; metastable β-Mn-type phase; spinning method; Rietveld analysis; CALPHAD method

Effect of silicide coatings on the mechanical properties of alloy 5VMTs by P. I. Glushko; B. M. Shirokov; A. V. Shiyan (616-618).
The paper examines the effect of silicide coatings and testing media on the strength and plasticity of alloy 5VMTs between 25 and 1100°C. It is established that uncoated samples tested in argon have higher strength and plasticity over the entire temperature range of interest than coated samples tested in argon and air. The major cause of decrease in the mechanical properties of coated samples is the silicide layer whose properties depend on testing temperature.
Keywords: silicide; ultimate strength; elongation; alloy; temperature; coating