Formation and annihilation of deformation twinning in hexagonal Ti with lamellar microstructure

The microstructural evolution and mechanical properties of Ti35 alloy applied in nuclear industry with lamellar microstructure during high-temperature straining were systematically investigated. Ti35 alloy plates were subjected to hot rolling down to 20 %, 50 % and 80 % reduction in thickness. Results showed that {101̅2}<101̅1̅>, {112̅2}<112̅3̅>and {101̅1}<101̅2̅>twins were developed during hot rolling and their proportion varied with the amount of deformation. The fraction of twinning boundary reached peak value in the 50 % reduction sample, which dominated by {101̅2}<101̅1̅>and {112̅2}<112̅3̅>twins. After annealing, the deformation twins in>50 % reduction samples were nearly annihilated. The twins and substructures acted as nucleation point for static recrystallization, resulting in twins annihilated and grain refinement during annealing. Micro-hardness and tensile tests revealed that deformation twinning improved strength and plasticity of the Ti35 alloy by introducing extra interfaces and reorientation.