Tailoring Microstructure of Selective Laser Melted TiAl-Alloy with In-Situ Heat Treatment via Multiple Laser Exposure

Intermetallic titanium aluminide (TiAl) alloys are considered attractive materials for high-temperature applications in aerospace, automotive, and energy industries. Additive manufacturing is a promising way of producing complex TiAl-alloy parts; however, it remains challenging due to brittleness of this alloy. While high-temperature preheating can mitigate cracking during selective laser melting, the microstructure of TiAl-alloys still needs to be optimized to achieve better mechanical performance. In this work, multiple laser exposures were used during selective laser melting of TiAl-based alloy to tailor its microstructure. Applying additional laser exposure of up to 20 times per layer induced an in situ heat treatment, which allowed to modify volume fraction and size of different phases. Microstructure, phase and chemical composition, and hardness of TiAl-alloys were investigsated with regards to several laser exposures during the selective laser melting process.