An athermal deformation model was proposed for the yield stress anomaly in Ni3Al based on the concept that dislocation multiplication versus the immobilization by the Kear-Wilsdorf locking controls the plastic deformation. In the model dislocations, super-kinks lying between two Kear-Wilsdorf locks multiply through expansion in an athermal manner. With regard to Kear-Wilsdorf locking, the entire screw segment cross-slipped onto (010) to form long Kear-Wilsdorf locks in one thermal activation event. The model could explain the macroscopic characteristics of the deformation, the strain-rate independent of the yield stress and the compliance with Schmid's law, which were recently revealed in binary, stoichiometric Ni3Al single crystals. Quantitative assessment proved that the model reproduces the temperature dependence of the yield stress with reasonable fitting parameters. The driving force for the Kear-Wilsdorf locking, one of the most important parameters for the yield stress anomaly, was evaluated at 127mJ/m2. This value was in good agreement with those calculated from the antiphase boundary energies on {111} and {100} reported in the literature.

An Athermal Deformation Model of the Yield Stress Anomaly in Ni3Al. Demura, M., Golberg, D., Hirano, T.: Intermetallics, 2007, 15[10], 1322-31