N. P. Leonova

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.

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.

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.

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

Metallography and electrical resistivity and hardness measurements are used to study the aging and recrystallization of Al-rich Al-Sc-Cr-Zr alloys with 0.1–0.4% Sc, 1.0% Cr, and 0.2% Zr. During aging at 350°C, the hardness of the alloys is found to increase substantially even after 0.5-h aging as compared to that of the deformed state. Variations of the hardness and electrical resistivity of all alloys exhibit similar behavior; however, the higher the scandium content in the alloys, the higher the strengthening effect reached after aging for 2–4 h. Combined small scandium, chromium, and zirconium additions to aluminum are shown to increase its recrystallization temperature; therewith, the effect of scandium on the increase in the temperatures of the onset and finish of recrystallization is more substantial.

Phase composition and mechanical properties of cerium- and yttrium-containing Al-Mg alloys subjected to heat treatments under various conditions

The phase composition and properties of Al-Mg-Ce and Al-Mg-Y alloys are studied by optical microscopy and mechanical-property measurements. Isothermal sections at 430 and 275°C that correspond to alloys having manganese concentrations of up to 16% and cerium and yttrium concentrations of up to 0.7% are constructed. The ultimate strength, yield strength, and relative elongation of quenched, worked, and aged Al-Mg-based alloys having 7.0–9.9% Mg and Ce, Y, Mn, and Zr additions are determined. The alloys are aged at 175, 200, 250, and 300°C; the time of aging corresponds to the maximum strengthening effect.

Phase composition of Al-Rich Al-Sc-Cr-Zr alloys at 640, 600, and 500°C

Metallographic and electron microprobe analyses and hardness and electrical resistivity measurements are used to study Al-rich Al-Sc-Cr-Zr alloys annealed and quenched from 640, 600, and 500°C. The boundaries of Al-based solid solution are determined; the Al-based solid solution is found to be in equilibrium with the CrAl7 compound and ScAl3- and ZrAl3-based phases, in which zirconium and scandium are dissolved, respectively. Sections of isothermal tetrahedra at 640, 600, and 500°C are constructed.

Scandium and yttrium solubilities in an aluminum-based solid solution at 500 and 600°C

Al-rich Al-Sc-Y alloys having up to 0.1 at % Sc and Y are studied by optical microscopy, X-ray diffraction, electron microprobe analysis, and electrical resistivity measurements. The solubilities of scandium and yttrium in solid aluminum and their effect on the electrical resistivity of the alloys annealed at 500 and 600°C are determined.

Structure and strength properties of the cold-deformed Al–Mg2Si-based alloys with additives of transition metals

Using methods of hardness measurements, determination of the tensile strength properties, and microstructure observation, the effect of annealing at various temperatures on structure and change in the strength properties of the cold-deformed Al–Mg2Si alloys alloyed with joint additives of scandium and zirconium is studied. It is shown that the hardness decreases with increasing annealing temperature to minimal values in the interval of 300–500°C and then increases up to 600°C. Such a change in hardness is explained by the recovery process (hardness decrease) and enrichment of the aluminum solid solution in magnesium and silicon followed by its natural aging (hardness increase). Addition of scandium and zirconium to the colddeformed Al–Mg2Si alloys promotes an increase in their strength properties both after aging of these alloys at 170°C for 16 h and after softening annealing at 400°C for 1 h.

Effect of additional doping with scandium and scandium with zirconium on strength properties of the alloys of Al–Mg2Si system

The effect of Sc and Sc + Zr on the structure and properties of Al–Mg–Si alloys is studied using the methods of hardness measurement, resistivity, mechanical properties, and light and electron microscopy. A considerable strengthening of Al–Mg2Si alloys doped with transition metals (Sc or Sc + Zr) during natural aging and its almost complete absence during artificial aging are established. The observed effects are explained using electron microscopy and local X-ray analysis.