Structure and mechanical properties of titanium subjected to high-rate channel angular pressing and deformation by rolling

Abstract

The macro- and microstructure have been analyzed and the tensile mechanical properties have been measured for commercial titanium subjected to dynamic channel angular pressing (DCAP) at high temperatures using one or two passes, as well as to additional warm rolling and low-temperature annealing. The structure of titanium after DCAP at a high temperature consists of a dispersed mixture of fine recrystallized grains (1 to 2 μm in size) and deformed nonrecrystallized regions. The deformed regions have a subgrain structure with sub-grains 200–300 nm in size. After the second pass, the size of the recrystallized grains becomes less by two times as compared to their size after one-pass DCAP, the subgrains in the deformed regions acquire a more equiaxed shape, and the microstructure becomes more uniform. The warm rolling of the samples subjected to DCAP at high temperatures increases the total density of dislocations and provides a high level of internal stresses. After two-pass DCAP at 530°C, the ultimate strength of titanium was 650MPa and the relative elongation was 19%. Additional rolling to 50% at 300°C and low-temperature annealing increases the ultimate strength to 790 MPa, while the relative elongation is retained at a high level of 15%.