Enhanced yield strength by fine grain strengthening and TRIP/TWIP effect of metastable β-type Ti-4 V-2Mo-2Fe alloy with high ductility

In this paper, we have obtained metastable β Ti-4 V-2Mo-2Fe (at. %) alloys with exceptional mechanical properties through the control of grain size. The microstructure analysis reveals that the reduction in grain size inhibits the formation of 332113 twins during deformation. The yield strength of the alloy can be significantly enhanced by reducing the grain size. When the grain size measures 13 μm, the alloy can achieve a yield strength exceeding 900 MPa due to the combined impact of fine grain strengthening in the recrystallized microstructure and dislocation strengthening in the non-recrystallized microstructure. Additionally, the work hardening capability and elongation of the alloy was enhanced effectively by the dynamic Hall-Petch effect induced by twins. The TRIP/TWIP effect significantly contributes to the work-hardening behavior and an impressive 24% elongation. The results of this study show that the deformation mechanism of metastable β titanium alloys could be affected by controlling grain size to achieve excellent strength-elongation balance, rendering the alloy promising for applications as structural materials.