Toward a Better Understanding of Phase Transformations in Additive Manufacturing of Alloy 718

Abstract

This paper presents a discussion on the phase-transformation aspects of additively manufactured Alloy 718 during the additive manufacturing (AM) process and subsequent commonly used post-heat treatments. To this end, fundamental theoretical principles, thermodynamic and kinetics modeling, and existing literature data are employed. Two different AM processes, namely, laser-directed energy deposition and electron-beam powder-bed fusion are considered. The general aspects of phase formation in Alloy 718 are first examined, followed by a detailed discussion on phase transformations during the two processes and subsequent heat-treatment. The information provided in this study will contribute to a better understanding of the overall process-structure-property relationship in the AM of Alloy 718.