Superplastic behavior of fine-grained Ti-10V-2Fe-3Al alloy fabricated by friction stir processing

Ti-10V-2Fe-3Al alloy with fine-grained β phases was fabricated by friction stir processing with optimized processing parameters. The superplastic behavior of the specimens was investigated by tensile deformation at different strain rates and temperatures, and an optimal superplastic elongation of 634% was achieved at 700°C and 3 × 10–4/s. An annealing treatment at 650°C for 60 min showed a microstructure with α precipitates distributed in the β matrix in the friction stir specimen. Such pre-heat treatment improves the superplasticity of the specimen, achieving an elongation of up to 807% at 750°C and 3 × 10–4/s. The influences of tensile temperatures and strain rates on the microstructural evolution, such as grain size variation, grain morphology, and phase transformations, were discussed. The superplastic deformation behavior of fine-grained Ti-10V-2Fe-3Al alloy is controlled by grain boundary sliding and accompanied by dynamic phase transformation and recrystallization.