Synergistic enhancement of strength and toughness of β-Ti alloy with a fine grain: Effect of deformation temperature

School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, PR China

^* Corresponding author: fanghongze@hit.edu.cn
^** Corresponding author: ruirunchen@hit.edu.cn

Abstract

It is difficult for as-cast titanium alloys to achieve high strength and toughness due to the presence of coarse β grains. In this study, multi-directional forging (MDF) was employed to break down the coarse β grains into fine grains and the mechanism of strengthening and toughening was also revealed. Results indicated that nearly all peaks corresponded to the β phase, with the α phase peaks being almost imperceptible. As the MDF temperature increased, the grain size initially decreased and then increased. All the dislocation is concentrated near the grain boundaries. The refinement of the grains can be attributed to the combined effects of mechanical crushing refinement and dynamic recrystallization. The tensile strength and fracture toughness is 1130 MPa and 82 MPa·m1/2. Grain refinement and dislocation proliferation caused by MDF are the main contributors to the improvement of strength and toughness in the alloys. This discovery lays a solid foundation for further research on new ultra-high strength and toughness titanium alloys, while also providing a new design concept for other high-performance alloys.