Impact of homogenization on microstructure-property relationships of Inconel 718 alloy prepared by laser powder bed fusion

Due to the temperature gradients generated from the complex heating and cooling cycles during Laser Powder Bed Fusion, strong columnar texture is often observed in the as-built Inconel 718 alloys together with notable residual stress, which leads to anisotropic properties of manufactured alloy components. We found that, in contrast to the typical homogenization performed at 1065°C, a simple higher temperature homogenization step conducted at 1180°C can effectively remove the residual stress and reconstruct the microstructure by introducing recrystallization. More importantly, it can introduce isotropic microstructures and tensile properties, which are critical in engineering applications. Additionally, owing to the elimination of the residual stress, the precipitation of the strengthening phase γ″ becomes more isotropic (i.e., with three variants precipitating) during the subsequent aging process. This work is conducive to developing effective post-heat treatment of additively manufactured alloys for better performance.