Study of substrate preheating on the microstructure and mechanical performance of Ti-15Mo alloy processed by selective laser melting

Abstract

The densification behaviors, microstructure and mechanical performance of Ti-15Mo alloy fabricated by selective laser melting (SLM) with various substrate preheating temperatures are investigated for the first time in this study. With the increase of the substrate preheating temperature, the risk of forming micro-cracks and keyholes is reduced, which is beneficial for high ductility, while the grain size is increased and the dislocation density is decreased, which is unconducive to obtaining high strength. The ultimate tensile strength and the ductility of the three samples reached 1134 ± 12 MPa, 8.36% ± 1.5% (room temperature), 854 ± 15 MPa, 25.75% ± 2% (100 ℃) and 841 ± 13 MPa, 30.39% ± 3% (200 ℃), respectively. The work-softening performance occurs in sample Ⅰ due to the generation of deformation twins being hindered by the ω phase. The appearance of lath-like {332}< 113 > deformation twins is responsible for the high work-hardening effect in samples Ⅱ and Ⅲ. The dislocation density is increased with the increase of strain and resultant enhanced dislocation strengthening, which is also one of the reasons for samples II and III showing an obvious work hardening.