High temperature deformation of Ti–(46–48)Al–2W intermetallic compounds

Abstract

The high temperature deformation behavior of Ti–46Al–2W and Ti–48Al–2W intermetallic compounds have been investigated in isothermal compressive tests, performed at temperatures between 1000°C and 1200°C for strain rates between 10 −3 and 10 −1 s −1. The stress–strain curve during high temperature deformation exhibits a peak stress which is followed by a gradual decrease into a steady state stress with increasing the strain. The flow softening behavior after the peak stress is attributed to the effects of dynamic recrystallization during deformation. The dependence of flow stress on temperature and strain rate followed a hyperbolic sine relationship using the Zener-Hollomon parameter. The activation energies, Q, were measured as 449 kJ mol −1 and 394 kJ mol −1, and the stress exponents were measured as 3.6 and 3.7 for Ti–46Al–2W and Ti–48Al–2W, respectively. The activation energy increased with decreasing Al content in TiAl-base intermetallic compounds. The coefficient between peak stress and Zener-Hollomon parameter, A, was not a constant, but was dependent on the activation energy. The peak stresses can be predicted well by using a normalized Zener-Hollomon parameter. The dynamic recrystallization rate and recrystallized grain size increased with increasing the temperature and with decreasing the strain rate.