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

Abstract

Compressive deformation of a metastable β titanium alloy (Ti–10V–2Fe–3Al) with different β grain sizes ranging from 109 μm to 494 μm was systematically investigated by using X-ray diffraction, electron backscatter diffraction and transmission electron microscopy techniques. As β grain size increases, the triggering stress of stress-induced martensitic transformation (β→α″) in Ti–10V–2Fe–3Al alloys gradually increases, while the amount of α″ 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 β grain sizes change from stress-induced martensitic transformation at small strains to stress-induced martensitic transformation, together with widening and merging of α″ martensite at large strains. Besides, {111}α″ type I internal twinning and {112}α″ type I deformation twinning are observed at Ti–10V–2Fe–3Al alloy with an average β grain size of 494 μm. During the compressive deformation, β matrix was repeatedly consumed and cut by α″ laths, leading to the formation of nano-sized α″ blocks and β blocks. This dynamic grain refinement contributes to a higher work hardening rate and enhanced compressive mechanical properties in the metastable β titanium alloy.