Low-Density Pulsed Current Induced Refinement of Secondary α Phase for Strengthening Ti-6Al-4V-0.5Mo-0.5Zr Alloy Without Sacrificing Ductility

Abstract:

Low-density short-duration pulsed current-assisted aging treatment was applied to the Ti-6Al-4V-0.5Mo-0.5Zr alloy subjected to different solution treatments. The results show that numerous α_p phases redissolve into the new β phase during the pulsed current-assisted aging process, and then the newly formed β phase is mainly transformed into the β_t phase, with occasional transition to new α_p phase, leading to a remarkable grain refinement, especially for the lamellar α_s phases. In comparison to conventional aging treatment, the pulsed current-assisted aging approach achieves a significant enhancement in strength without degrading ductility, yielding an excellent mechanical property combination: a yield strength of 932 MPa, a tensile strength of 1042 MPa, and an elongation of 12.2%. It is primarily ascribed to the increased fraction of β_t phases, the obvious grain refinement effect, and the slip block effect induced by the multiple-variant α_s colonies distributed within β_t phases.