Effect of Build Orientation on Mechanical Properties and Microstructure of Ti-6Al-4V Manufactured by Selective Laser Melting

Ti-6Al-4V with five build orientations relative to the substrate (0, 30, 45, 60, and 90 deg) prepared by selective laser melting (SLM) process was studied. Four distinct conditions were considered: as-built without any treatment, heat treatment below the beta-transus, hot isostatic pressing, and heat treatment above the beta-transus. The effect of build orientation on the mechanical properties and microstructure of SLM Ti-6Al-4V was comprehensively analyzed from the aspects of residual stress, pore distribution, texture, and microstructure. The results revealed that the residual stress, pore distribution, and texture were the main contributors to the differences in mechanical properties among samples with different build orientations. The tensile strength of samples in the as-built state reaches a maximum and minimum at 45 deg (1134 MPa) and 90 deg (1004 MPa), respectively. The elongation of SLM Ti-6Al-4V material reaches a maximum of 10 pct for the 0 deg sample because of its lower porosity and a minimum of 3.5 pct for the 45 deg sample due to its high porosity. The 0 deg sample in the as-built state exhibits the longest fatigue life because of its lower porosity and adequate strength, and the 90 deg sample exhibits the shortest fatigue life because of its lowest static strength caused by high residual stress.