Tensile Deformation Behavior of a Heterogeneous Structural Dual-Phase Metastable β Titanium Alloy

BCC-β phase stability significantly affects the mechanical properties of metastable β titanium alloys. In this study, a dual-phase metastable β titanium alloy with different β phase stabilities was fabricated by solution treatments to tailor the volume fraction of the α phase. With decreasing volume fraction of the α phase, the structural stability of the β phase and the triggering stress for stress-induced martensitic transformation decrease. With the decrease in volume fraction of the α phase, multistage work hardening is observed in the dual (α + β) phases and the single β phase alloy, resulting from the sequentially activated stress-induced martensitic transformation and multi-type twinning in β phase and α″ martensites. Dual-phase metastable β titanium alloy with the α phase fraction of 25.9 pct has a good balance of strength and ductility. The hetero-deformation-induced (HDI) hardening and transformation-induced plasticity (TRIP) are discussed by loading–unloading–reloading (LUR) tensile experiments and microstructure observation, respectively. This finding provides a new design to tune the HDI stress in metastable β titanium alloys.