Twinning and its effect on the evolution of acicular α in Ti-5AI-5Mo-5V-3Cr-1Zr

摘要

Near fi titanium alloy Ti-5AI-5Mo-5V-3Cr-1Zr with acicular α microstructure was hot compressed at 750°C/10~(-3) s~(-1). Twinning and its effect on the evolution of acicular α were investigated. Twinning is induced from the dislocations pile-up at α/β boundary. The twinning system is (1101 )/[1102]. During twinning, one type of pure shear displacement and three types of shuffle + shear mixed displacement are confirmed. The twinning dislocation can be expressed as (b,4h0), ρ_e~(1101) = ρ_e~(1101)[1102], ho is the interplanar distance of (1101), ρ_e~(1101) = (4k~2 - 9)/(3 + 4k~2), k = da. Substructures form in acicular α through the migration of twin boundary, followed by meeting another neighbouring parallel twin and then causing the twins-merging. And the accumulation of the twinning displacement results in the bending of acicular α.