Microstructural characteristic and mechanical property of Ti6Al4V alloy fabricated by selective laser melting

Ti6Al4V parts with near-full 98.3% density, significantly refined microstructures and attendant obviously improved mechanical strength were fabricated by SLM additive manufacturing. The cellular prior β grains were formed on XY plane. However, the columnar morphology of prior β grains were formed on the XZ and YZ planes, which showed an epitaxial growth along the building direction through successive deposited layers. All the planes displayed the fine acicular α′ martensites formed due to the significantly rapid cooling rate of melt pool. The reason for forming the intersection angular of 40°-50° between acicular α′ and β boundaries was clarified. The improved tensile strength of 1261 MPa and good ductility with elongation of 10.2% were simultaneous obtained for SLM-processed Ti6Al4V part. The present work provides a fundamental understanding of rapid manufacturing of high-strength and light-weight structural materials by laser additive manufacturing.