Improved mechanical properties of high strength titanium alloy with bi-lamellar microstructure via in-situ heat treatment during additive manufacturing

High strength titanium alloy is one of the important types of titanium alloys that widely applied in aerospace and aviation industries. With the demand of complex parts and rapid near net shaping been proposed these years, the performance of these alloys under additive manufacturing (AM) methods are gained more attention. However, due to the relatively low phase stability of beta-matrix, such alloys are suffering from extreme fine alpha precipitate and low elongation in as-built state which require complex post-processing treatments to satisfy the design performance. In this study, two typical AM processes with different energy input are carried out to study the mechanical performance as well as strengthening mechanism of high strength Ti-5Al-4Cr-4Mo-4V-3Zr alloy. By utilizing high energy input and low cooling rate during the AM process, samples manufactured via high-energy electron beam melting (HE-EBM) developed a bi-lamellar heterogeneous microstructure, resulting in an averaged ultimate tensile strength of 1152 MPa with an elongation of 13.8 %. These mechanical properties are comparable to those of the alloy in its forged state after solution and aging treatment. The overall findings could provide further insight for the future AM techniques and applications of near-beta and beta titanium alloys.