Hot deformation characteristics of Ti-22Al-25Nb alloy using processing maps

The hot deformation characteristics of Ti-22Al-25Nb alloy have been studied in the temperature range of 940°C-1060°C and strain rate range of 0.001 s^-1-10 s^-1 using processing maps developed on the basis of dynamic material model (DMM). The results show that the alloy exhibits a wide instability regime due to cracking or shear band formation at a strain rate greater than 1 s^-1. At lower temperatures (940°C-970°C), the instability is characterized by shear cracking along 45° orientation with respect to the compression axis and adiabatic shear band formation. At higher temperatures (970°C-1060°C), the instability is attributed to longitudinal cracking or flow localization. The others are safe regimes characterized by recrystallization. This alloy exhibits lathy α₂/O spheroidization in the temperature range of 940°C-970°C and strain rate range of 0.001 s^-1-0.4 s^-1 with a power dissipation efficiency of about 35%. The deformation characteristics of Ti-22Al-25Nb alloy in the temperature rang of 970°C-1060°C and strain rate range of 0.001 s^-1-1 s^-1 are continuous recrystallization with a power dissipation efficiency of about 35%-45%. This alloy has a peak efficiency of 45%-66% at 1030°C-1060°C and 0.001 s^-1-0.1 s^-1, which is attributed to the growth of continuous recrystallized grains.