[en] Data on phase equilibria in binary and termary systems formed by molybdenum with carbon ad 4 group transition metals: titanim, zirconium, hafnium are presented. The results of investigations are given, and literature data on this problem published in Soviet and foreign press up till 1982 are systematized

[en] The phase equilibria in the W-Hf-C ternary system from subsolidus temperatures to 1400 deg C and the reactions during crystallization of the alloys have been studied by metallographical and X-ray analyses. The experimental data were used to construct the following polythermal cross-sections: HfC-WCsub(0.39), HfC-WCsub(0.43), HfC-WCsub(0.51), HfC-WCsub(0.61), HfC-WCsub(0.64), HfC-WCsub(0.75), HfC-WC. None of these cross-sections is quasibinary; all of them possess a complex structure. Therefore the interaction between tungsten carbides and hafnium carbides is to be discussed on the basis of the data on phase equilibria in the Hf-W-C ternary system

[en] The methods of radiography of crystalline grains isolated from annealed (1170 K) alloys are used to study a low temperature modification of Nb₂C (βsub(r)-Nb₂C) with rhombically distorted structure as against high-temperature HCP-phase (β). It is shown that the βsub(r)-phase in the frames of an elementary cell of the metal atom lattice is hereditary-oriented relative to the initial β-phase in compliance with the correlation. Actual sizes of superstructural rhombic elementary cell βsub(r)-Nb₂C are determined for the first time

No abstract available

[en] Methods of X-ray phase and metallographic analyses as well as those of microhardness measurement were applied to study the structure of cast alloys of the binary W-C and ternary W-(Ti, Zr, Hf)-C systems containing from 36 to 45 at.% of carbon and up to 4 at.% of alloying metals. It is shown that in the mentioned ternary systems within the studied range of compositions as well as in the binary W-C system there occurs an incongruent crystallization of the hexagonal higher tungsten carbide WC following the reaction L+C reversible WC and a congruent combined crystallization of cubic and hexagonal carbides L reversible α-(W, Me(4))Csub(1-x)+WC. Small additives (up to 2 at %) of group 4 metals are stated to increase essentially microhardness of high-disperse structure components

[en] The phase equilibria in the Sc-Zr-C system were investigated for the first time using metallography, differential thermal analysis (DTA), X-ray powder patterns (XRD), and electron probe microanalysis (EPMA). The projections of the solidus and liquidus surfaces were constructed. A continuous solid solution was found to form between isomorphous (NaCl-type) carbides of scandium and zirconium. As the thermodynamically most stable phase, the δ-NaCl-type phase is in equilibrium with all the phases that exist at subsolidus temperatures. The microhardness of this phase at the carbon-rich boundary of the homogeneity range decreases monotonously from 2970 kg mm^-2 for ZrC_1-x to 1100 kg mm^-2 for ScC_1-x. There are two four-phase incongruent-type equilibria with participation of the liquid phase: L+δ+β-Sc₄C₃<->Sc₃C₄ (1810 C) and L+δ<->Sc₃C₄+C (1737 C). (orig.)

[en] Data on constitutional daigrams of limiting systems, metal-chemical and thermodynamic properties of components and carbides permit constructing hypothetical projections of solidus surfaces for constitutional diagrams of Sc-Ti(Zr, Hf, V, Nb, Ta, Cr, Mo, W, Re, Tc)-C. The prediction is based on the criteria previously found by the authors for formation of continuous series of solid carbide solutions of the NaCl type, saturation of the NaCl type phases with carbon and tie line equation by E. Rudy. The prediction is experimentally confirmed for Sc-Cr-C and Sc-Mo-C systems

[en] The diagram, reflecting the condition of the Er-Ge system condition, has been plotted for the first time. Confirmed were the following phases: Er₅-Ge₃(melts congruently), Er₅-Ge₄, Er-Ge, Er-Ge₅, Er-Gesub(3-x). A new compound (Er-Ge₂) has been revealed, which melts incongruently. The Sc-Mo system is of an eutectic type. The eutectic temperature is 1.190 deg C. Cubic (20-40 at. % C) and tetragonal (45-55 at. % C) carbides have been found in the Sc-C system cast alloys. In the Sc-Mo-C system, cubic carbides of scandium and molybdenum form a continuous series of solid solutions, that are strongly scandium-enriched in equilibrium with the Mo-based phase. The W-Hf-C and W-Zr-C systems alloy crystallization diagrams have been plotted. Also, the isothermic profile of the Ti-Ni-Mo system at 900 deg C has been plotted. The triple phase which is isomorphic with respect to Ni₃Mo has been detected. All the intermediate phases are in equilibrium with Mo-based solid solutions. In the V-Re-Zr system, ZrRe₂ dissolves 45 mol. % ZrV₂, while ZrV₂ dissolves 40 mol. % ZrRe₂. No structural transformations have been spotted in the alloy in the solid solution. The V-Re-Zr system alloys show promise for the nuclear technology

[en] Short note

[en] The thermodynamic description of the ternary system Al-B-Ti is obtained by modelling the Gibbs energy of all individual phases in the system using the CALPHAD approach. The model parameters have been evaluated using the computer optimization technique PARROT based on the available descriptions of the constituent binary systems Al-B, B-Ti and Al-Ti recently published and relevant experimental information on phase equilibria for the ternary system. For the ternary system Al-B-Ti the reaction scheme, projection of the liquidus, solidus and solvus surfaces, selected vertical and isothermal sections are calculated using the proposed thermodynamic description. An acceptable agreement between the calculations and experimental data is achieved