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

In this paper, we have obtained metastable beta Ti-4V-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 {332}(113) twins during deformation. The yield strength of the alloy can be significantly enhanced by reducing the grain size. When the grain size measures 13 mu m, 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 beta titanium alloys could be affected by controlling grain size to achieve excellent strength-elongation balance, rendering the alloy promising for applications as structural materials.