Microstructure evolution and mechanical behavior of ultrafine Ti[sbnd]6Al[sbnd]4V during low-temperature superplastic deformation.

The influence of microstructure evolution on the low-temperature superplasticity of ultrafine Ti 6Al 4V was established. For this purpose, the static and dynamic coarsening response and plastic-flow behavior of the alloy with a mean size of α (sub)grains and β particles of 0.1–0.4 μm were determined via a series of tension tests at temperatures between 450 and 700 °C. Both static and dynamic coarsening exhibited diffusion-controlled ( r 3 -vs-time) kinetics. However, dynamic coarsening was approximately two orders of magnitude faster than the corresponding static behaviors due to enhanced diffusion through the deformed β matrix. A total elongation of 1000% and strain-rate-sensitivity exponent m = 0.48 were obtained at 550 °C and 2 × 10 −4 s −1 . Very limited cavitation was observed in the specimens after superplastic deformation under optimal conditions. [ABSTRACT FROM AUTHOR]