Increasing the yield strength while preserving strain hardenability and ductility in a beta titanium alloy exhibiting transformation induced plasticity (TRIP)

The commercial β-Ti alloy, Ti-10V-2Fe-3Al; primarily used with an α+β microstructure, exhibits a high yield strength but with poor strain-hardenability and limited ductility. This paper focuses on the interplay between stress-induced martensite (α”) in this alloy, introduced via prior cold-rolling (5,10, 20, and 30%) and additional martensite (α”) forming during subsequent tensile loading, leading to a simple way to substantially increase the yield strength while enhancing the high strain hardenability (via TRIP) and maintaining the uniform tensile ductility. The results indicate that the YS in this alloy can be substantially tuned from 400 to 1800 MPa, via cold-rolling. Among the various conditions that were analyzed, the 5% cold-rolled condition offered the best combination of YS (∼900 MPa), ductility (8%) and the strain hardenability. The stress-induced α” formation during tensile loading is essential for maintaining the high strain-hardening and, consequently the uniform tensile ductility in this alloy.