Structure and Motion of Misfit Dislocations at Ni/Ni3Al Interface : Molecular Dynamics Study

Abstract

For a new insight on the misfit dislocation networks in Ni-based superalloys, we investigate the structure and motion of misfit dislocations on two different semi-coherent interfaces between Ni and Ni3Al, Interface 1 and 2, by using molecular dynamics simulations. The former does not have Al atoms at the interface in the Ni3Al side, while the later does. Misfit dislocation networks are actually found on the interfaces along the and directions, as observed in experiments. Detail observation of the dislocation cores reveals that the network is basically composed of the edge dislocation ; however, Interface 1 also shows screw character at the intersections of the network. By applying the tension normal to the interfaces, many partial dislocation loops nucleate and propagate from the network on Interface 1, first in the Ni side then in the Ni3Al side. Partial loops are also originated from the network of Interface 2 into the Ni3Al side; however, they make dislocation locking with another partial on the conjugate slip plane, showing wedge-like stacking faults parallel to the network. Partial loops also nucleate and expand from the networks on both interfaces, only into the Ni3Al side under the compression normal to the interfaces. The dislocation locking is not found under the compression, while the partials originate a little faster from the network on Interface 1 than that of Interface 2.