Synergistic strengthening and toughening in β titanium alloy via enhanced micron-sized primary α with the fiber-like β grains
Leliang Liu, Qiaoyan Sun, Jixiong Liu, Xiaoxiang Wang, Jun Sun
Abstract
• A fiber-like structure in a high-strength metastable β titanium alloy was architected to synergistically enhance the strength, ductility and toughness. • An excellent balance of tensile strength, ductility and impact toughness (1434 MPa, 11.7 %, 47.3 J/cm 2 ) was obtained. • The kink bands formed during thermomechanical process strengthened the micron-scale primary α phase. • The influence of fiber-like microstructure on the crack propagation mode during Charpy impact tests is analyzed. The trade-offs between strength and toughness and strength and ductility restrict the broader use of high-strength titanium alloys. To optimize the coordination of strength, ductility and toughness, a fiber-like structure in a metastable β titanium alloy was architected through a simple thermomechanical process and aging treatment. During the thermomechanical process, the microscale primary α phase (α p ) hindered the migration of β grain boundaries and coordinated the deformation, forming fiber-like β grains. The fiber-like β grains effectively hinder and deflect crack propagation in Charpy impact tests, significantly enhancing the impact toughness. Meanwhile, plenty of kink bands activated in the α p after the thermomechanical process, refining the α grains and resulting in high yield strength and ductility. The impact toughness of the fiber-structured titanium alloy rises from 28.3 ± 2.5 J/cm 2 to 47.3 ± 2.8 J/cm 2 when compared to the sample with a bimodal structure, while the yield strength and elongation remain at the same level. The design of Fiber-structured titanium alloys synergistically enhances the strength, ductility and toughness of the Ti-Al-Mo-V-Cr-Nb titanium alloy, providing a novel way to coordinate the strength, ductility and toughness of high-strength titanium alloy.