A strategy for simultaneously enhancing the strength and ductility of metastable β titanium alloys: Coupling heterogeneous structure and TRIP effects

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2024-11, Vol.915, p.147264, Article 147264
• Main Authors: Feng, Tengfeng, Luo, Zhengyang, Ma, Xinkai
• Format: Article
• Language: English
• Subjects: HDI hardening; HDI stress; Heterostructure; Metastable β titanium alloy; TRIP
• ISSN: 0921-5093
• DOI: 10.1016/j.msea.2024.147264

The applicability of metastable β titanium alloys is frequently constrained by their relatively low yield strength. This study has successfully designed a metastable β titanium alloy with heterogeneous microstructures (HS) comprising both deformed and recrystallized grains, achieved through simple cold rolling followed by short-term annealing. Compared to traditionally coarse-grained (CG) specimen that is entirely crystallized and equiaxed, the HS specimen exhibit not only a postponed initiation of double yielding but also superior yield strength (enhanced by 27.8 %) and ductility (enhanced by 7 %). The delayed double yielding and enhanced strength in the HS specimen are ascribed to the restriction of dislocation motion by α" martensite and the heterogeneous deformation induced (HDI) strengthening mechanisms. The ductility of the HS specimen exceeds that of the CG specimen, owing to the combined effect of HDI hardening and the transformation-induced plasticity (TRIP) effects. The more pronounced TRIP effect in the HS specimens results from the synergistic effect of the elevated HDI stress and the applied external stress, which promotes the occurrence of stress-induced martensitic phase transformation. This study offers a novel strategy for the development of high-performance metastable β titanium alloys.