A unique {332}<113> twin to α″ martensite transition during twin propagation in a Ti-12wt.% Mo alloy with micro-segregation

In this study, the propagation behavior of {332}<113>β twins was investigated in a Ti-12Mo (wt.%) alloy with micro-segregation bands (Mo content ranging from 10 to 13 wt.%). A unique transition from {332}<113>β twins to α"-martensite was observed when those twins propagated across the Mo-lean bands inside the grain. A deflection angle of ∼18° was found between the twin boundary and the α"-martensite plate. This transition was more frequently found at relatively higher stresses. Thermodynamic analysis revealed that the Mo content together with the applied stress govern the required mechanical work for triggering α" martensitic phase transformation. The stress-induced α" martensitic phase transformation was easier to trigger in the Mo-lean bands, with a spontaneous interruption of the {332}<113>β twin propagation. The present chemically segregated microstructure provides a novel approach to comprehensively characterize the variable deformation modes in metastable β titanium alloys.