Selective laser melting of Ti-22Al-25Nb intermetallic: Significant effects of hatch distance on microstructural features and mechanical properties

Ti-22Al-25Nb (at.%) intermetallic is a light weight, high performance, high temperature material with density of merely (similar to)60% of Ni-based superalloys. The advent and rapid development of selective laser melting (SLM) enable direct fabrication of the Ti-22Al-25Nb intermetallic into complex geometry parts, promising for various critical applications. This paper is dedicated to better understanding the effects of hatch distance, an important but often underestimated processing factor, on microstructure and mechanical properties of the SLM-prepared Ti-22Al-25Nb. Along with analytical means such as transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD), finite element simulation has also been employed to explore the underlying mechanisms. It is determined that the highest mechanical properties are achieved at a hatch distance of 0.16 mm due to the following factors: (a) High density dislocation, (2) favorable phase features, and (3) high relative density. As-fabricated parts of micro-turbine engine using the optimized parameters are provided in the end of the study to demonstrate the capability of SLM to manufacture high quality and delicate structural parts of the Ti-22Al-25Nb intermetallic.