Compressive deformation of a metastable β titanium alloy undergoing a stress-induced martensitic transformation: The role of β grain size

Compressive deformation of a metastable beta titanium alloy (Ti-10V-2Fe-3Al) with different beta grain sizes ranging from 109 mu m to 494 mu m was systematically investigated by using X-ray diffraction, electron backscatter diffraction and transmission electron microscopy techniques. As beta grain size increases, the triggering stress of stress-induced martensitic transformation (beta ->alpha '') in Ti-10V-2Fe-3Al alloys gradually increases, while the amount of alpha '' martensite decreases, along with the gradual disappearance of double yield behavior in compressive stress-strain curves and three-stage behavior of work hardening rate and exponent. Deformation mechanisms of Ti-10V-2Fe-3Al alloy with different beta grain sizes change from stress-induced martensitic transformation at small strains to stress-induced martensitic transformation, together with widening and merging of alpha '' martensite at large strains. Besides, {111}(alpha '') type I internal twinning and {112}(alpha '' )type I deformation twinning are observed at Ti-10V-2Fe-3Al alloy with an average beta grain size of 494 mu m. During the compressive deformation, beta matrix was repeatedly consumed and cut by alpha '' laths, leading to the formation of nano-sized alpha '' blocks and beta blocks. This dynamic grain refinement contributes to a higher work hardening rate and enhanced compressive mechanical properties in the metastable beta titanium alloy.