Atomistic analysis of temperature-dependent dislocation dynamics in Ni3Al-based intermetallic alloys

In this study, we investigate the dynamics of superlattice edge dislocations composed of partial dislocations, complex stacking faults, and antiphase boundaries in binary and ternary Ni-based alloys (& gamma;' phase) with the L12 structure. In the case of Ni3Al, the dislocation velocity decreases with increasing temperature at low applied shear stress, mainly owing to the phonon drag effect. Meanwhile, in the case of ternary alloys constructed by exchanging Ni atoms with Co atoms in Ni3Al, the effects of temperature on dislocation motion are more complex. At low applied shear stress, the dislocation motion is disturbed by solute Co (i.e., solid-solution strengthening). In this case, the temperature promotes dislocation motion because the potential energy barrier dominates the thermally activated dislocation dynamics. In contrast, when the applied shear stress increases, the temperature suppresses dislocation motion owing to the phonon drag effect. The drag effect also increases with increasing Co concentration. The origin of the energy barrier due to solute atoms at low applied shear stress can be explained by the interaction between the partial dislocation and solute Co. Meanwhile, the origin of the drag effect on the superlattice dislocation dynamics is discussed on the basis of atomic vibrational motions and wavy dislocation behaviors. In this study, we propose and construct a map showing the dominant effects on complex superlattice dislocation dynamics. The map has energy-barrier-dominated, phonon-drag-dominated, and sound velocitydominated regions, suggesting that the dominant factor changes depending on the applied shear stress, temperature, and strength of the solute-dislocation interaction.