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

BCC-beta phase stability significantly affects the mechanical properties of metastable beta titanium alloys. In this study, a dual-phase metastable beta titanium alloy with different beta phase stabilities was fabricated by solution treatments to tailor the volume fraction of the alpha phase. With decreasing volume fraction of the alpha phase, the structural stability of the beta phase and the triggering stress for stress-induced martensitic transformation decrease. With the decrease in volume fraction of the alpha phase, multistage work hardening is observed in the dual (alpha + beta) phases and the single beta phase alloy, resulting from the sequentially activated stress-induced martensitic transformation and multi-type twinning in beta phase and alpha '' martensites. Dual-phase metastable beta titanium alloy with the alpha 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 beta titanium alloys.