The structure and mobility of super-dislocations in Ir3X (X = Ti, Zr, Hf, V, Nb, Ta) with L12 structure were investigated within the framework of the modified Peierls-Nabarro model with first-principles generalized stacking fault energetics calculated using the all-electron full-potential linearized augmented plane wave method. Superlattice intrinsic stacking fault-bound super-dislocations (Kear splitting scheme) were strongly preferred energetically in Ir3V, Ir3Nb, and Ir3Ta, whereas antiphase boundary-bound super-dislocations (Shockley splitting scheme) were predicted in Ir3Ti, Ir3Zr, and Ir3Hf. Because antiphase boundary-bound super-dislocations were considered to be responsible for the yield stress anomaly, the results predicted that positive yield stress temperature dependence could only be expected in Ir3Ti, Ir3Zr and Ir3Hf; with a negative one in Ir3V, Ir3Nb and Ir3Ta. The relationship of the mechanical behavior of the Ir3X alloys to the L12 → D019 structural instability was established and its electronic origin was analyzed.

Dislocation Structure, Phase Stability, and Yield Stress Behavior of L12 Intermetallics - Ir3X (X = Ti, Zr, Hf, V, Nb, Ta). O.Y.Kontsevoi, A.J.Freeman, Y.N.Gornostyrev, A.F.Maksyutov, K.Y.Khromov: Metallurgical and Materials Transactions A, 2005, 36[3], 559-66