Microstructure control and high-temperature mechanical response of TA15 titanium alloy fabricated by selective laser melting

In this study, the TA15 titanium alloy specimen was manufactured by selective laser melting (SLM) technology. The forming mechanism and microstructure of SLM-produced TA15 components were analyzed by numerical simulations and experimental methods. Abaqus software was employed to clarify the temperature field characteristics during SLM process, and a thermal conduction model was developed. The results showed that the peak temperature within melt pool exceeds the β-transus during SLM, which promotes dynamic recrystallization and Widmanstätten α structures. The microstructure of the SLM-produced TA15 components was almost entirely composed of the α phase, with the β phase present in only 0.6 % and 0.5 % in scanning and building directions, respectively. The microstructure exhibited a high degree of uniformity, with grains displaying various orientations, and grains had no obvious local plastic deformation with few substructures. In the SLM process of TA15 titanium alloy, rapid temperature fluctuations are observed, accompanied by uniform heat distribution and symmetrically arranged temperature field centered around the heat source. The temperature gradient ahead of the heat source is less steep than that behind it. Additionally, the tensile test of TA15 titanium alloy produced by SLM was carried out at 500 °C, microscopic holes are generated at grain boundaries. The specimen had obvious plastic deformation before tensile fracture, and fracture mode was mainly ductile fracture. It was worth noting that the tensile strength of the specimen exceeds 800 MPa, and hardness of the samples is similar in two directions, with an average hardness of 420.2 ± 12.6 HV and 400.6 ± 22.5 HV, showing that TA15 titanium alloy processed by SLM has excellent mechanical properties.