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

Near beta titanium alloy Ti-5Al-5Mo-5V-3Cr-1Zr with acicular alpha microstructure was hot compressed at 750 degrees C/10(-3) s(-1). Twinning and its effect on the evolution of acicular alpha were investigated. Twinning is induced from the dislocations pile-up at alpha/beta boundary. The twinning system is . 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, 4h(0)), , h(0) is the interplanar distance of , , kappa = c/a. Substructures form in acicular alpha 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 alpha.