Challenges during laser Powder Bed Fusion of a Near-Alpha Titanium Alloy - Ti-6242Si

Ti-6Al-2Sn-4Zr-2Mo-Si (Ti-6242Si) is a near-α phase titanium alloy that has a greater strength up to 565 °C compared to the workhorse Ti-6Al-4V alloy with a typical service temperature of up to 400 °C. While there is a wealth of literature to help understand the laser powder bed fusion (LPBF) of Ti-6Al-4V, only a few research articles about LPBF of Ti-6242Si are available in the open literature. In this work, LPBF processing diagrams and temperature prediction models were used to investigate the impact of process parameters such as laser power, scan speed, and beam spot radius on macroscale characteristics of the builds such as density and surface roughness. The use of processing diagrams allowed for exploration of density ranges between 99.55-99.98 %, and surface roughness, Sa, ranges between 8-16 μm in Ti-6242Si processed by LPBF. Cracking in Ti-6242Si manufactured by LPBF is reported for the first time. Cracking during LPBF of Ti-6242Si was observed to strongly depend upon the predicted melting mode (conduction, transition, and keyhole) for a given set of LPBF process parameters.