In situ synchrotron diffraction study of a crack-free additively manufactured Ni base superalloy

Abstract

The tensile deformation behaviour of a crack-free additively manufactured (AM) Ni base superalloy and its wrought (W) counterpart has been investigated by in-situ synchrotron X-ray diffraction. In order to understand the evolution of dislocation character, dislocation density (ρ), coherent scattering domain size (D) and dislocation arrangement parameter (M), the diffraction data corresponding to the first six{hkl} reflections have been analyzed using modified Williamson-Hall and modified Warren-Averbach methodologies. The ρ was found to be relatively higher in AM superalloy as compared to W superalloy during both the regimes of elastic and plastic deformation. In the plastic deformation regime, while the fraction of edge and screw dislocations was found to be nearly equal in proportion in W superalloy, the fraction of screw dislocations remained higher in AM superalloy. In view of the relatively high initial ρ and inefficacy of D in AM superalloy, heat treatment in as-built parts is suggested.