Effect of heat treatment on the microstructure and mechanical properties of Ti6Al4V gradient structures manufactured by selective laser melting

In this research, a body-center-cubic (BCC) gradient porous structure has been designed. Selective laser melting (SLM) was used to fabricate the Ti6Al4V BCC gradient porous structures. The effects of different heat treatments on the microstructure and mechanical properties were investigated by X-ray diffraction, scanning electron microscopy and compression tests. The microstructure morphologies show that α laths became coarser and amount of nano-sized β particles decreased after higher temperature solution heat treatment. The fracture morphologies show that fracture mechanism of Ti6Al4V gradient porous structure changed from brittle fracture to ductile fracture after heat treatment at 800 °C for 120 min and furnace cooling (SLM800FC). The energy absorption mode can be optimized by solution heat treatment and the energy absorption at ε = 50% of SLM800FC is 76.40 ± 12.65 MJ/m3, which is the highest value among the five group. These findings suggest that the gradient structure and specific heat treatment can improve the stability and predictability of Ti6Al4V porous structure.