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 degrees C similar to 1060 degrees C and strain rate range of 0.001 s(-1)similar to 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 degrees C similar to 970 degrees 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 degrees C similar to 1060 degrees C), the instability is attributed to longitudinal cracking or flow localization. The others are safe regimes characterized by recrystallization. This alloy exhibits lathy alpha(2)/O spheroidization in the temperature range of 940 degrees C similar to 970 degrees C and strain rate range of 0.001 s(-1)similar to 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 degrees C-1060 degrees C and strain rate range of 0.001 s(-1)similar to 1 s(-1) are continuous recrystallization with a power dissipation efficiency of about 35%similar to 45%. This alloy has a peak efficiency of 45%-66% at 1030 degrees C-1060 degrees C and 0.001 s(-1)similar to 0.1 s(-1), which is attributed to the growth of continuous recrystallized grains.