Hybrid manufacturing (HYAM) for refined DLD’d Ti-6Al-4V

The typical thermal history during the additive manufacturing process (instrinct directional cooling) could causes the formation of large columnar grains in Ti-6Al-4V. These large columnar grains with length up to several centimeters are detrimental to the tensile properties and more importantly, the fatigue properties. This could make additive manufactured Ti-6Al-4V less attractive for the industry. In this study, a hybrid manufacturing method (HYAM) by in-situ micro-rolling the deposited material during powder feed direct laser deposition (DLD) process was established to break up the large columnar piror-β grains in Ti-6Al-4V. The results showed that consistent and small prior-β grains were formed through the entire sample made by this hybrid manufacturing method. Furthermore, the tensile strength and ductility on both directions (horizontal and build directions) were improved and the mechanical property anisotropy was eliminated. This hybrid manufacturing method offers an efficient way to refine the microstructures of DLD'd Ti-6Al-4V and improve its mechanical properties.