Strain rate sensitivity in a metastable β-Ti alloy with stress-induced martensitic transformation: Role of ω phase on yield strength

This study investigated the effect of strain rates on the stress-induced martensitic transformation (SIMT) and mechanical properties of a Ti-15Nb-5Zr-4Sn-1Fe metastable (3-Ti alloy, with a focus on the role of the w phase on the initial activation of SIMT at the onset of yielding. The results demonstrated that increasing the strain rate from 5 x 10_ 4 s_ 1 to 1 x 10_ 1 s_ 1 enhanced the yield strength while reducing ultimate tensile strength and strain-hardening ability due to the slightly suppressed SIMT. The presence of dispersed w nanoparticles within the (3 matrix impeded the initial activation of long-range SIMT without preventing its occurrence, which partially contributed to the increased yield strength with increasing strain rate. Once the long-range SIMT was activated at higher stress levels, SIMT proceeded more readily, causing a more pronounced stress plateau and more homogeneous formation of martensite across different (3 grains at higher strain rates. These findings emphasize the significant influence of the w phase on the activation of SIMT under high strain rate deformation. Controlling the w phase could potentially regulate SIMT and optimize the mechanical properties of metastable (3-Ti alloy for high strain rate deformation.