Effect of stress-induced martensite volume fraction on deformation behavior and mechanical properties of Ti-7333 alloy

In the present work, the evolution of stress-induced martensite transformation under various deformation reductions was investigated, and the effects of martensite volume fractions on subsequent deformation behaviors were assessed. The cold rolling deformation was performed at ambient temperature, and the deformation reductions are 2%, 5%, and 10%, respectively. At a reduction of 2%, the presence of deformation bands and sparse martensite within the grains resulted in a yield strength of 545 MPa and an elongation of 16.3%. When the reduction was increased to 10%, a yield strength of 773 MPa and an elongation of 12.3% were observed. As stress increased, an increase in the martensite quantity and 5 types of martensitic variants are produced, which facilitated the accommodation of deformation. It was found that the volume fraction of martensite significantly influenced subsequent deformation behaviors. When the martensite volume fraction in the matrix is relatively low, the subsequent deformation process is primarily dominated by stress-induced martensite transformation. when the volume fraction is elevated, martensite twins predominantly manifest within the interior of the martensite, primarily exhibiting the {111}(alpha") type I twinning. When the martensitic transition approaches saturation, a significant occurrence of {130} <310>a" compound twinning is observed. The observed martensite and twin transformation indicate complex microstructure evolution during deformation. The multistage coordination of formed martensitic twins can effectively improve the properties. The results show that the regulation and control of martensite volume fraction can markedly affect the deformation behavior of metastable beta titanium alloys.