Superplasticity of Sintered Titanium Alloy with Martensitic Structure

The behavior of superplastic deformation in a sintered Ti-4mass%Cr alloy with martensitic structure (martensitic material) was examined in connection with the structural change during tensile test at elevated température. The martensitic material has the maximum elongation of about 300% at 1023K, in spite of containing about 6vol% of pores. During tensile testing, fine equiaxed duplex structure is formed from martensitic structure characterized by acicular a' grains, and it is confirmed that such a structural change is realized with the assist of mechanical shear and that, without deformation, equiaxization of acicular a' grains does not occur. The formation of fine equiaxed duplex structure make the grain boundary sliding possible, and this leads to an appearance of superplasticity.