High-temperature deformation behavior of the extruded Ti-22Al-25Nb alloy fabricated by powder metallurgy

The hot-deformation behavior of the extruded Ti-22Al-25Nb alloy was investigated by compression testing in the 1213-1333 K temperature range, under a 0.001-1.0 s(-1) strain-rate range. The activation energy, Q, at a deformation strain of 0.3, was calculated to be 574.80 kJ mol(-1). A strain-compensated Arrhenius-type constitutive model was established for this alloy, with an average absolute relative error (AARE) and correlation coefficient (R) of 7.64% and 0.994, respectively. Based on the dynamic materials model (DMM), processing maps were developed by combining the power dissipation and instability maps. An instability region was identified in the 1213-1278 K temperature range and 0.022-1.0 s(-1) strain-rate range. The microstructure of specimens deformed under different conditions were analyzed to characterize the corresponding deformation mechanisms. The main softening mechanisms in the stability regions were dynamic recrystallization (DRX) and dynamic globularization. The grain size of the specimen deformed at 1313 K/0.001 s(-1) was approximately 15.2 mu m.