Temperature and crystal orientation dependence of dislocation slip and twin nucleation in bilayer Ni/Ni3Al interface

Abstract

Plastic deformation of nickel-based single crystal superalloy has obvious crystal orientation dependence. Mechanical properties and microstructural evolution behaviors were studied by molecular dynamics (MD) in [0 0 1], [0 1 1] and [1 1 1] crystal orientation. Temperature and crystal orientation dependence of dislocation slip and twin nucleation was observed in nickel-based single crystal superalloys. We found [1 1 1] crystal orientation has the best mechanical properties and next the [0 0 1] crystal orientation, the least [0 1 1] crystal orientation at the same temperature. As the temperature increases, the gap of interface dislocation network density decreases. Dislocation slip is the foremost way of deformation of [0 0 1] crystal oriented nickel-based single crystal superalloy under different temperature conditions. We found that the Lomer-Cottrell dislocation in γ' phase is an important factor affecting its strength. [0 1 1] crystal orientation exhibits significant yield behavior and work-hardening during stretching. When the temperature is 1000 K or less, twinning occurs during stretching. Combination of twinning and dislocation slips forms a zigzag of stress-strain curves, which provides a theoretical explanation for the experimental observation. Deformation mechanism of [1 1 1] crystal orientation is dislocation slip. This study will provide theoretical guidance for the application of nickel-based single crystal alloys and further enhancement of their mechanical properties.