3D-EBSD characterization and anisotropic grain grow simulation of additive manufactured IN718

International audienceThe relationship between microstructure and properties has been well established through the years. Although, many characteristics can be evaluated from two-dimensional (2D) images, there is a wide number of aspects that cannot be fully described in this way, such as a complete characterization of grain morphology, real shape of second phase particles and twin descriptors. A microstructure is indeed three-dimensional (3D) by nature and a full description of the aspects previously named requires a characterization in the 3D space. Additive manufactured IN718 has a complex microstructure that cannot be fully described using 2D material characterization methods. The as-built microstructure is basically composed of elongated grains, approximately 300µm in the building direction, mixed with smaller and more equiaxed grains (equivalent diameter around 30µm), a high number of twins and porosity. Therefore, there is an imperious need to carry out a 3D characterization that allows a better understanding of the microstructure evolutions, such as grain growth during thermal treatment following the building step. In this study, an as-built additive manufactured IN718 is characterized in 3D by means of a mechanical serial sectioning. This procedure consists of two main steps. A vibratory polishing and electron backscattered diffraction (EBSD) analyses were sequentially performed. Then, all the images were post-processed, and the three-dimensional reconstruction is obtained using Dream3D. Finally, the reconstruction is immersed in a finite element level-set framework and grain growth simulations that consider anisotropic grain boundary energy and mobility are carried out