Role of Processing in Microstructural Evolution in Inconel 625: A Comparison of Three Additive Manufacturing Techniques

Additive manufacturing (AM) processes have widely varying thermal environments, which dictate the solidification of alloys during solidification. Here, we use binder jet 3D printing (BJ3DP), electron beam freeform fabrication (EBF3), and direct metal laser sintering (DMLS) to fabricate samples of Inconel 625, displaying the significant differences in microstructure brought about purely by the thermal gradients produced in each manufacturing method. Dislocation density and elastic strain are measured using high-resolution electron backscatter diffraction and the spatial relationship between these features is analyzed with respect to the relative thermal environments of each AM technique, with DMLS exhibiting microstructure typical of high thermal gradients and rapid solidification. Increasing thermal gradient and solidification rate results in a stronger spatial dependence of microscale elastic strain on GND density. Our results also demonstrate the use of statistical techniques to quantify microstructural features in relation to processing, which has potential for informing frameworks which can predict microstructure and material properties of AM components.