Effect of heat treatment on the modification of microstructure of selective laser melted (SLM) IN718 and its consequences on mechanical behavior

In this investigation, the superalloy IN718 has been prepared by additive manufacturing (AM) following a selective laser melting technique, and the post-AM heat treatments have been optimized. The microstructure of additively manufactured (AM) IN718 is characterized by the presence of dendritic and cellular features with large spatial heterogeneity along and across the build plane. Along the build direction, the fiber texture dominates. Heat treatment involving two-step solution treatment, and subsequently, two-step aging treatment was specifically designed to facilitate the precipitation of d phase at the grain boundaries to make the material resistant to grain boundary sliding (GBS). The AM IN718 showed dynamic strain aging (DSA) at three different temperatures, while the critical strain for the onset of serration was extended to a higher value after the heat treatment.