Effect of Scanning Strategy on Additively Manufactured Ti6Al4V

This study investigates the influence of different scanning strategies on the hardness of the parts, fabricated by direct metal laser melting. In this work, prealloyed powder of titanium alloy (Ti-6Al-4V) is used to produce dense parts with three different scanning strategies: unidirectional, alternate, and cross-hatching. A numerical scheme is developed to predict the heat transfer, fluid flow, and thermal history-based phase transformation during the process. Surface hardness is calculated from the obtained phase fractions. Hardness is measured experimentally, and X-ray diffraction is used for phase identification. The hardness is found to be highly dependent on the microstructure of as-built parts. The results show that rapid solidification during direct metal laser melting leads to the formation of hcp-structured acicular martensite from the parent beta phase, which increases the hardness. Higher part densities are observed for cross-hatching strategy compared to other scanning strategies. The predicted maximum hardness for different scanning strategies compare well against the experimental observations.