N. R. Bochvar

Phase composition and recrystallization of Al-based Al-Sc-Mn-Zr alloys

The phase composition and recrystallization of Al-based alloys with small amounts (up to 4 wt %) of transition metals, such as Sc, Mn, and Zr, are studied by metallography and electrical resistivity and hardness measurements. No new phases, besides phases in equilibrium with an Al-based solid solution in the associated ternary systems, are found for the portion of the quaternary Al-Sc-Mn-Zr system under study. It is also found that the manganese and zirconium solubilities in the Al-based solid solution decrease in the presence of scandium and that zirconium additions in Al-Sc-Mn alloys increase their recrystallization temperature.

Structure and properties of Cu-Cr alloys subjected to shear under pressure and subsequent heating

The effects of the chromium content (0.75, 9.85, 27%) in Cu-Cr alloys, their initial state, and the heating temperature on their thermal stability after severe plastic deformation are studied by microhardness and electrical resistivity measurements and metallography. The microhardness and electrical resistivity of Cu-Cr alloys are determined as functions of the heating temperature in the range 50–600°C, and microhardness distributions over the diameter of samples differing in the chromium content are plotted. The difference in the strengthening and softening of low- and high-alloy copper-chromium alloys subjected to high-pressure torsion is shown to be related to the initial structure of the material.

Behavior of an ultrafine-grained Cu-Zr alloy in heating

The effect of the heating temperature and the initial state (annealed or quenched) of a Cu-0.18% Zr alloy subjected to severe plastic deformation on its microhardness and electrical resistivity is studied. The microhardness distribution along a sample diameter and the dependences of the microhardness and electrical resistivity on the heating temperature in the range from 50 to 550°C are plotted. It is shown that the hardening of Cu-0.18% Zr alloy samples after torsion under hydrostatic pressure is stable up to 400°C irrespective of their initial structure.

Effect of yttrium and chromium on the recrystallization of Al-Sc alloys

The effect of small chromium and yttrium additions (0.14–1.0 wt%) on the recrystallization of Al-Sc alloys having 0.1–0.4% Sc is studied with polarized light. The microstructure of cold-rolled samples annealed at 100–630°C for 1 h is examined. The chromium and yttrium additions are found to slightly affect the recrystallization temperature of the Al-Sc alloys: they increase or decrease it slightly depending on the scandium content.

Phase equilibria in Al-rich Al-Sc-Cr alloys

Phase equilibria in aluminum alloys containing up to 1.2 wt % Sc and 1.0 wt % Cr are studied by optical microscopy and differential thermal and electron microprobe analyses. Two vertical sections and the projection of liquidus surface have been constructed. The four-phase nonvariant equilibrium at a temperature of 656.5 ± 1°C is found to have a transition character. The Al-based solid solution is found to be in equilibrium only with the Al3Sc and Al7Cr binary phases.

Al-rich portion of the Al-Hf phase diagram

Electrical resistivity measurements, differential thermal analysis, optical microscopy, and the deposition of hafnium compound particles from a melt are used to study the Al-rich portion of the Al-Hf phase diagram. Prominence is given to the hafnium solubility in solid and liquid aluminum. The studies show a peritectic character of the invariant reaction during the solidification of alloys with sufficiently high hafnium contents and a slight difference between the peritectic and melting temperatures of pure aluminum. The hafnium solubility in solid and liquid aluminum is shown to increase with the temperature. The hafnium solubility in solid aluminum at the peritectic temperature (maximum solubility) is 1.00 wt % (0.153 at %); the hafnium solubility in liquid aluminum at this temperature is 0.43 wt % (0.065 at %).

Joint effect of scandium, manganese, and chromium on the recrystallization of aluminum alloys

The joint effect of manganese and chromium additions (0.25–0.8 wt %) on the recrystallization of Al-(0.1–0.4 wt %) Sc alloys is studied. The recrystallization is studied using changes in the microstructure of the alloys annealed in the temperature range 100–630°C. Depending on the scandium content in the alloys, combined alloying of them with manganese and chromium is found to lead to a slight increase or decrease in the recrystallization temperature of the Al-Sc alloys.

Phase equilibria in the ternary Al-Sc-Mn system

Optical microscopy, electron microprobe analysis, and electrical resistivity measurements are used to study Al-Sc-Mn alloys containing up to 3 at % Sc and to 2.5 at % Mn. The boundaries of the Al-based solid solution are determined at 640, 600, and 400°C, and the isothermal section of the Al-rich portion of the Al-Sc-Mn system at 640°C is constructed. The Al-based solid solution is found to be in equilibrium with the ScAl3 and MnAl6 phases.

Thermodynamic evaluation of the Cu-Mg-Zr system

The thermodynamic evaluation of the Cu–Mg–Zr system is presented in this paper. A literature survey was carried out first based on the most recent literature, which was scanned from the THERMET literature database. The evaluation of the thermodynamic parameters was carried out using Thermo-Calc (version H) software. The evaluation of the Cu–Mg–Zr system was carried out using the most recent experimental data from the literature and a set of DTA measurements. DTA measurements were done using alumina (Al2O3) crucibles under helium atmosphere with the niobium (Nb) reference crucible. The evaluated Cu–Mg–Zr phase diagram fitted well with experimental data with the liquidus data in a limited range of composition. There were two miscibility gaps observed in the system. New τ phase was detected using the X-ray and microscopic analysis and the data was used in this evaluation.

Decomposition kinetics of the supersaturated solid solution in Al-Mg2Si alloys with scandium, zirconium, and hafnium additions

The decomposition kinetics of the aluminum-based supersaturated solid solution in Al-Mg2Si alloys with some transition metal additions is studied by hardness and electrical resistivity measurements, optical microscopy, and scanning electron microscopy. The effect of only scandium or scandium along with zirconium and hafnium on the hardening of the Al-Mg-Si alloys after heat treatment, which includes quenching, natural aging, and artificial aging, is revealed. The artificial aging temperature at which the hardening is maximal is chosen.