Toward an Index for Predicting Additive Manufacturability of Refractory High-Entropy Alloys

Abstract

Computational screening metrics through which the additive manufacturability of novel refractory high-entropy alloys can be rapidly assessed are investigated, with a focus on laser powder bed fusion. The rapid heating and cooling experienced in both laser powder bed fusion and laser directed energy deposition additive manufacturing techniques result in a processing regime that differs from conventional casting- and welding-based hot crack susceptibility metrics. Calculation of phase diagrams (CALPHAD) is used to predict possible phases, alloy compositions, and freezing ranges for a database of 100 alloys published in the literature, and it is shown that several established metrics can differ substantially from one another. A new additive manufacturing cracking susceptibility criterion is proposed, based on Pearson correlation with cumulative crack lengths observed in laser glaze experiments on selected alloys. Equilibrium freezing range was most correlated with cumulative crack length (Pearson r = 0.89), followed by the Scheil freezing range (r = 0.84) and Pugh’s G/B ratio (r = – 0.90). Combined metrics, such as further improved predictive capability with correlations. Established crack susceptibility indices like Kou CSI (r = 0.54) and Clyne CSC (r = -0.86) were found to be less predictive for RHEAs under LPBF conditions.