Orientation dependence of plastic deformation in nickel-based single crystal superalloys: Discrete-continuous model simulations

The anisotropic mechanical response of single-crystal nickel-based superalloys is simulated. At 1123 K, two uniaxial tensile loading cases are simulated: one along [0 0 1] and another along [1 1 1]. Resulting stress-strain curves, stress distributions, interfacial dislocation structures are analysed. In accordance with experiments, the simulations show an anisotropic yield strength. The applied strain is accommodated by dislocations propagating through matrix channels on octahedral slip systems. The net result appears as slip bands along the cubic directions, even though no cubic slip systems are activated. In the [0 0 1] case, the plastic flow is distributed more or less evenly among the three matrix channels, whereas in the [1 1 1] case it is mainly concentrated in one single channel. Typical zig-zag configurations are observed. The elementary mechanisms controlling their formation are explained. Cross-slip does not play any role there. The hardening anisotropy between both loading cases is related to strong differences between the interfacial dislocation microstructures. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.