Superplastic behavior of a TiAl-based alloy

Superplastic behavior under the conditions of a temperature range from 850 to 1075 degrees C and strain rates varying from 8x10(-5) to 1 x 10(-3) s(-1 ) was investigated for Ti-33Al-3Cr-0.5Mo (wt%) alloy with a very fine grain size obtained by the multi-step thermal mechanical treatment. The results show that the TiAl-based alloy with a hot-deformed fine grain size possesse s good superplasticity. It exhibits a strain rate sensitivity coefficient o f 0.9 at a strain rate of 3 x 10(-5) s(-1) and temperature from 1000 to 107 5 degrees C. Moreover, the strain rate sensitivity coefficient is stable du ring the hot deformation, and a tensile elongation of 517% was obtained at 1075 degrees C and a strain rate of 8 x 10(-5) s(-1). The superplastic beha vior of the present fine-grained TiAl-based alloy can be explained by the l ocal strain hardening and high m value during the tensile deformation. Micr ostructure evolution in the superplastic deformation was also discussed. (C ) 2000 Elsevier Science Ltd. All rights reserved.