Effect of Process Induction on Densification Behavior, Microstructure Evolution and Mechanical Properties of Ti-5al-2.5sn Eli Fabricated by Laser Powder Bed Melting

Abstract

In this paper, Ti-5Al-2.5Sn ELI α titanium alloy was prepared by laser powder bed fusion. The effects of heat treatment and HIP process on the densification behavior, microstructure evolution, low temperature mechanical properties and fracture behavior of Ti-5Al-2.5Sn ELI titanium alloy were analyzed. The experimental results show that the density of Ti-5Al-2.5Sn ELI titanium alloy is significantly improved after heat treatment and HIP treatment. Complete recrystallization occurred in the deposited microstructure, and the recrystallized α grains coarsened with the increase of holding time. After heat treatment, the tensile strength decreases gradually, while the elongation increases with the increase of holding time. Compared with 300 K, the ultimate tensile strength and yield strength of the sample at 77 K were improved, but the elongation decreased. Ti-5Al-2.5Sn ELI titanium alloy annealed at 850 °C/4 h exhibits mixed ductile-brittle fracture morphology at 77 K and obtains ultrahigh strength and ductility. At the same time, Ti-5Al-2.5Sn ELI titanium alloy exhibits unit slip deformation behavior at 300 K, while at 77 K, it mainly exhibits the coupling of dislocation slip and twin deformation behavior. These findings lay a foundation for the rapid preparation of high-strength α-titanium alloy products with good ductility.

Keywords: Laser powder bed melting, Ti-5Al-2.5Sn ELI, Microstructure, Deformation mechanism