Deformation mechanisms of additively manufactured Hastelloy-X: A neutron diffraction experiment and crystal plasticity finite element modeling

The development of strong textures can affect mechanical anisotropy in the specimens produced by the laser powder bed fusion (LPBF) additive manufacturing (AM) technique. In this study, in-situ neutron diffraction experiments were conducted on nickel superalloy specimens to understand how mechanical ansitropy and the evolution of internal strains are affected by changing the LPBF-AM parameters. In addition, Electron Backscatter Diffraction (EBSD) measurements were performed to characterize the initial microstructure of the specimens. The measured EBSD maps were imported into a crystal plasticity finite element (CPFE) model to further study how different AM parameters, specifically laser power and scanning speed, affect the development of internal strains. At higher specific energy (SE) inputs, columnar grains are observed, and samples developed a 〈1 1 0〉 texture along the building direction and a 〈1 0 0〉 texture along the scanning direction, while at lower SEs random texture is observed. The development of texture affects elastic and plastic anisotropy, as well as the development of internal strains in different directions, particularly for the {2 0 0} lattice strains measured in the laser scanning direction. It is shown that (1 1 1) 〈1 1 0〉 slip system is the most active one for the range of applied strains.