In-situ study of adjacent grains slip transfer of Inconel 718 during tensile process at high temperature

Abstract

Adjacent grains slip transfer is an important mechanism for metal adaptation to incompatibilities in intergranular deformation. Thus, this paper investigates slip transmission at grain boundaries (GBs) and annealed twin boundaries (TBs) in Inconel 718 (IN718) alloy using in-situ tensile test at 650 °C by integrating slip trace analysis and the crystal plasticity finite element method (CPFEM). Results show that the mαβ criterion, based on the match of intersection lines between slip planes to GB planes and slip directions, is more reasonable in predicting induced activated slip systems than Luster-Morris mαβ′ criterion. In addition, slip transfer tended to occur at mαβ′>0.83 and Δb(1/b)<0.44 or mαβ>0.82 and Δb(1/b)<0.46 for general GBs; when mαβ′>0.92 or mαβ>0.93, continuous slip transfer is a crucial mechanism to coordinate strain and reduce stress concentration. Furthermore, the acceptable criteria for slip transfer at TBs are θ≈0 and Δb(1/b)<0.6 by experimental and computational results. This study deepens the understanding of the adjacent grains slip transfer behavior of IN718 and also provides a new strategy to study the deformation behavior of Nickel-based superalloys.