Recrystallization behavior and martensitic transformation in Ti-7Mo-3Nb-3Cr-3Al alloy: Impact on work hardening transition

This study focuses on the microstructure evolution and mechanical properties of Ti-7Mo-3Nb-3Cr-3Al alloy after cold rolling (20 %, 50 % and 70 % reductions) and subsequent annealing. The analysis includes recrystallization kinetics, activation energy, and the influence of recrystallization on work hardening behavior at varying degrees of recrystallization. Cold deformation generates deformation bands and stress-induced martensite; with increasing strain, banded structures become irregular. Following recrystallization annealing treatment, recrystallized grains preferentially form at grain boundaries and adjacent to deformation bands within recovered regions. At 870°C, the recrystallization kinetics follow the equation: Xr _(870 °C) = 1 − exp (−0.0773 × t^1.79), with an activation energy of 120.95 kJ/mol. Mechanical properties and work-hardening behavior are strongly correlated with the recrystallized grain size. The average grain size of recrystallization increases to about 115 μm, accompanied by the disappearance of the double-yield phenomenon, at about 40 μm, the observed double-yielding correlates with changes in the amount and variant selection of stress-induced martensite. Variations in work hardening behavior are primarily influenced by the recrystallized grain size and by the amount and variant selection of martensite.