Deformation mechanisms of hard oriented NiAl single crystals

Abstract

Hard oriented NiAl single crystals (<100> deformation axis) have been compressed at temperatures between 296K and 963K. At about 600K the yield stress changes from a plateau to a steep fall. Slip line investigations show that this coincides with a transition from {112}<111> to {110}<110> slip. At low temperatures slip of <111> dislocations is determined by the Peierls mechanism while in the plateau region the deformation mechanism is still not understood. For the deformation by {110}<110> slip the activation enthalpy measured supports the deformation mechanism proposed by Mills et al. [1] based on the diffusion-assisted motion of macro-kinks in <110> edge dislocations which are found to be decomposed into <100> edge dislocations. The slip transition temperature is discussed with regard to the brittle-to-ductile transition temperature of polycrystalline NiAl. © 2010 IOP Publishing Ltd.