Breaking Strength-Ductility Trade-off Relation in Ti-38644 Alloy with Heterogeneous Bi-Grain Bi-Lamella Structure

Abstract Metastable β titanium alloy is an ideal material for lightweight and high strength due to its excellent comprehensive mechanical properties. However, overcoming the trade-off relation between strength and ductility remains a significant challenge. In this study, the mechanical properties of Ti-38644 alloy were optimized by introducing a heterogeneous bi-grain bi-lamella (BG-BL) structure through a well-designed combination of rolling, drawing and heat treatment. The results demonstrate that the present BG-BL Ti-38644 alloy shows a tensile strength of ~ 1500 MPa and a total elongation of 18%. In particular, the high strength-elongation combination of the BG-BL Ti-38644 alloy breakthroughs the trade-off relation in all the titanium alloys available. The recrystallized grains with low dislocation enhance the ductility of the Ti-38644 alloy, while the highly distorted elongated grains mainly contribute to the high strength. The present study provides a new principle for designing Ti alloys with superior strength and ductility.