High strain rate deformation of Ti-48Al-2Nb-2Cr in the duplex morphology

The compressive deformation behavior of Ti-48Al-2Nb-2Cr in the duplex microstructural morphology has been studied at strain rates of 0.001/s and 2000/s over the temperature range from -196 to 1100°C. The material was cast, homogenized, extruded and heat treated to obtain the duplex microstructure. The yield stress is strain rate sensitive at 25°C and increases with temperature at a strain rate of 2000/s from 500 to 1100°C. TEM investigations reveal that deformation occurs in γ-TiAl by means of {111}〈112〉 twinning, 1/2 〈110〉 slip, and 〈101〉 superdislocations under all conditions depending on the orientation of the grain with respect to the deformation axis. Optical metallography reveals that twinning increases with increasing strain rate. TEM results revealing the dislocation substructure are used to explain the yield stress anomaly.