Microstructure and Mechanical Property of Ti–5Al–5Mo–5V–3Cr–1Zr Alloy Fabricated by Selective Laser Melting with a Preheated Substrate

Abstract

The high solidification rate of selective laser melting (SLM) induces a nonequilibrium microstructure in as‐fabricated Ti alloys. Herein, a metastable β Ti–5Al–5Mo–5V–3Cr–1Zr alloy is successfully fabricated by SLM on a preheated substrate at 700 °C. The effects of preheating temperature on microstructure and mechanical properties of as‐fabricated specimens is systematically studied. The phase identification and electron microscopic results demonstrate that the 700 °C preheating temperature enables the transformation of metastable β structure into an α + β structure with massive amounts of nanosized α precipitates. Consequently, the SLM‐fabricated specimen after preheating process possesses higher ultimate tensile strength and hardness at 1440 MPa and 8.24 GPa, respectively. This work shows an alternative for SLM to tackle nonequilibrium microstructure and to increase the strength of metastable Ti alloys by introducing high temperature preheating.

Recent innovations in laser additive manufacturing of titanium alloys

“…The substrate heating is able to reduce residual stress (figures 13(c)and (d)) and improve ductility (figures 13(g) and (h)). For metastable β-Ti alloys, the substrate heating can be used to promote the β→α phase transformation and suppress the formation of an unfavourable ω phase, which is favourable for achieving higher strength and hardness [145,149,150]. Figures 13(i) and (j) present the microstructure of LPBF Ti-5Al-5V-5Mo-3Cr alloy processed with substrate heating at 500 • C. The substrate heating promotes the formation of numerous fine α precipitates during LPBF (figure 13(k)), which greatly enhances the strength of the alloy (figure 13(l)).…”