Unusual stress-induced martensite transformation in Ti-6Al-4V alloy enabled by solution treatment in the lower α+β regime

• Published in: Journal of alloys and compounds 2023-09, Vol.956, p.170330, Article 170330
• Main Authors: Zhou, Xuefeng, Li, Yulin, Han, Ziru, Liu, Zilin, Liu, Kaiwen, Tu, Yiyou, Fang, Feng, Jiang, Jianqing
• Format: Article
• Language: English
• Subjects: Metastable β phase; Strain hardening; Stress-induced martensite transformation (SIMT); Ti-6Al-4 V; Transformation-induced plasticity (TRIP)
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2023.170330

Ti-6Al-4V alloy commonly suffers from low strain hardening capability and limited ductility. The present study proposes a novel pathway for improving its work hardening capacity via simple solution in the virgin lower α + β regime. Systematical investigations on microstructures and mechanical properties were conducted to unveil the underlying mechanism. Elemental partitioning occurs between α and β phases and β-stabilizers are progressively depleted from β phases as solution temperature rises. Metastable β phases (βm) can be created in the range of 550 ∼ 700 °C and transform into α′′ martensite during mechanical straining. The unusual stress-induced βm → α′′ martensite transformation (SIMT) in Ti-6Al-4V alloy induces three-staged strain hardening and triggers the highly desired transformation-induced plasticity (TRIP) effect. Such merit endows this alloy with an extremely high strain hardening rate of ∼6.5 GPa and ensures good combinations of strength and ductility. ●The correlation between solution microstructures and strain hardening in the mysterious lower α + β regime alloy is unveiled.●Unusual stress-induced martensite transformation occurs, producing the transformation-induced plasticity effect.●An extremely high strain hardening rate of 6.25 GPa is achieved, inducing an increment of total elongation by 46%.