Heat treatment of titanium manufactured by selective laser melting: Microstructure and tensile properties

Excellent mechanical properties, including residual stress, ductility and strength, are important requirements for bone implants. In order to achieve this effect, titanium samples were manufactured by selective laser melting, and the prepared parts were subsequently subjected to three different heat treatment, which were 550 °C, 650 °C and 750 °C for 2 h, respectively. The results show that for as-built sample, relatively short lath-shaped α grains and a few needle-shaped α′ grains were present. After heat treatment, the α grains became thicker and longer, and the α′ grains became more. As the heat treatment temperature increases from 550 °C to 750 °C, the size of the lath-shaped α grains gradually decreases, and the small-sized needle-shaped α′ grains become denser. Moreover, the tensile strength, elongation and shrinkage of specimens increased as the heat treatment temperature increased. The fine microstructure of heat-treated samples also significantly promoted the improvement of tensile properties. The fracture mechanism of the specimens changed from brittle fracture to a mixed mode including ductile and brittle fracture, so that the tensile strength and ductility of the heat-treated specimens were well combined.