Eliminating segregation defects during additive manufacturing of high strength β-titanium alloys

Abstract

Segregation defects, known as β-flecks, have long detracted from the widespread use of metastable β-Titanium alloys produced via solidification routes. These defects form when segregated β-stabilising solute such as chromium create localised phase instabilities which is detrimental to the alloy’s aging response and mechanical properties. This work explores whether Additive Manufacturing is a viable process for preventing the formation of these defects in the Beta-C alloy (Ti-3Al-8V-6Cr-4Mo-4Zr). Although it is observed that β-flecks initially form during deposition of the top layer, each new subsequent layer and thermal cycle promotes solid-state diffusion of alloy elements that effectively heals the segregation defect. Additive Manufacturing is thus a promising pathway for producing high quality metastable β-titanium alloys free of this defect.