An attempt was made to clarify the effects of the anisotropy of the antiphase boundary energy upon the yield-stress anomaly of 5 distinct Ni3(Ti,Nb) single crystals with various long-period ordered structures in which the antiphase boundary energy on the non close-packed plane varied with changes in the stacking sequence of the close-packed planes. The antiphase boundary energies of interest were estimated, based upon a pair-wise interaction up to second-nearest neighbour. The yield-stress anomaly could be categorized into 2 groups of 2 and 3 compounds; within which the mechanical properties were almost independent of composition. The microstructures which resulted from deformation at 700C were compared. It was confirmed that the yield-stress anomaly was predominantly controlled by differences in the probability of locking by a Kear-Wilsdorf mechanism; which itself was governed by the anisotropy of the antiphase boundary energy in the non close-packed planes, relative to the primary slip plane.

Effects of the Anisotropy of the Anti-Phase Boundary Energy on the Yield-Stress Anomaly in Ni3X Compounds with Close-Packed Crystal Structures. K.Hagihara, T.Tanaka, T.Nakano, P.Veyssière, Y.Umakoshi: Philosophical Magazine Letters, 2007, 87[10], 705-12

Table 11

Diffusivity of 63Ni in Ni2MnGa