Insights into fracture behavior of Ni-based superalloy single crystals: An atomistic investigation

Abstract

Comprehending the plastic deformation and failure mechanisms in Ni-based superalloys is vital to enhance their intrinsic ductility. In view of this, the present work intends to illustrate the complex deformation mechanisms ensued during tensile deformation of pre-cracked Ni-Ni3Al single crystals using atomistic simulations. Simulations of fracture, thermodynamic continuum treatments of crack initiation and detailed calculations of crack propagation toughness are performed synergistically to analyze the competition between dislocation emission and cleavage. This competition is evaluated under Mode-I loading for 18 different pre-cracked configurations (three different crack lengths, three phase orientations and two phases) in totality. Our results demonstrate that dislocation as well as twin plasticity eventuate and the competition between the two plastic modes depends on the crystallographic orientation of the abutting phases. Higher initial crack lengths can otherwise lead to cleavage like propagation in the material; however this does not imply inferior ductility of the system as long as the phase boundary lies in the path of advancing crack. Changes in configurations in terms of pre-cracked phase or initial crack lengths can engender appreciable differences in the elementary crack tip phenomena. The numerical computations of crack propagation toughness are compared favorably well with the available experiments in the literature. The calculated variations in overall toughness of the material are discussed and analyzed in light of the observed deformation landscapes.