Microstructure and Properties of Ti-6Al-4V Alloy Formed byElectron Beam Selective Melting at Different Deposition Heights

Ti-6A1-4V alloy sheet with a thickness of 10 mm was prepared by electron beam selective melting. Change of microstructure, tensile properties and microhardness of the alloy along the deposition direction was studied. The results show that the alloy structure was mainly composed of α clusters and a mesh basket structure with interlaced α sheets. Due to multiple thermal cycles, the α sheets at the bottom were slightly coarser than those at the top. The width of the primary β crystals increased slightly with the increase of deposition height. The yield strength and tensile strength of the bottom, middle and top of the alloy showed a gradually increasing trend, but the difference was small. Tensile specimens at different deposition heights all showed ductile fracture. There were voids and unmelted spherical powder at the fracture. The average hardness of the top of the alloy (about 315 HV) was slightly higher than that of the bottom (about 295 HV), and the hardness after tension slightly increased due to the strain hardening effect.