Enhanced microstructural homogeneity and strength-ductility synergy of Ti-6Cr-5Mo-5V-4Al β-titanium alloy wires through boron addition

One of the long-term concerns regarding titanium alloy wires involves microstructural inhomogeneity, mechanical instability and product unreliability in service. In this study, a strategy of micro-alloying was utilized to address the issue in Ti-6Cr-5Mo-5V-4Al (Ti6554) beta-titanium alloy wires. The microstructures and mechanical properties of Ti6554 hot-rolled wires were optimized through boron (B) additions. The results manifest that B-addition promotes microstructural homogenization of wires, wherein the microstructure nearly completely consists of normal grain region (NGR) without abnormal grain region (AGR) like that in the B-free alloys. This microstructural homogenization relieves mechanical fluctuation amongst different samples and renders plastic flow highly repeatable upon stretching. Meanwhile, B-addition strengthens wires whilst maintains decent ductility and thereby achieves the better combination of strength and ductility in comparison with that in the B-free wires. The analyses indicate that the addition of B facilitates the universal occurrence of dynamic recrystallization (DRX) to form NGRs at the expense of AGRs, which is beneficial to microstructural homogenization of hot-rolled wires. A good plastic accommodation resulting from NGRs and strengthening caused by TiB laths endow Ti6554 wires superior strength-ductility synergy. These findings provide helpful guidance for microstructural and performance optimization of titanium alloy wires.

Automated summary

In this study, boron (B) additions were used to optimize the microstructure and mechanical properties of Ti-6Cr-5Mo-5V-4Al (Ti6554) hot-rolled wires. The addition of B promoted microstructural homogenization of the wires, reducing mechanical fluctuations and achieving a better combination of strength and ductility. The addition of B facilitated dynamic recrystallization (DRX) and benefited the microstructural homogenization of the wires. These findings provide helpful guidance for the microstructural and performance optimization of titanium alloy wires.