New Development in Selective Laser Melting of Ti-6Al-4V: A Wider Processing Window for the Achievement of Fully Lamellar α plus β Microstructures

Recent progress has shown that Ti-6Al-4V fabricated by selective laser melting (SLM) can achieve a fully lamellar alpha + beta microstructure using 60 A mu m layer thickness in the as-built state via in situ martensite decomposition by manipulating the processing parameters. The potential to broaden the processing window was explored in this study by increasing the layer thickness to the less commonly used 90 A mu m. Fully lamellar alpha + beta microstructures were produced in the as-built state using inter-layer times in the range of 1-12 s. Microstructural features such as the alpha-lath thickness and morphology were sensitive to both build height and inter-layer time. The alpha-laths produced using the inter-layer time of 1 s were much coarser than those produced with the inter-layer time of 12 s. The fine fully lamellar alpha + beta structure resulted in tensile ductility of 11% and yield strength of 980 MPa. The tensile properties can be further improved by minimizing the presence of process-induced defects.