THE ACTIVATION-ENERGY FOR (111) CROSS-SLIP IN L1(2) ORDERED ALLOYS

The activation energy for octahedral cross-slip of superdislocations i n L1(2) ordered alloys from a (111) glide plane into a (1 (1) over bar 1) cross-slip plane is calculated in a three-dimensional treatment. B y approximating the bow-outs in the two superpartials by piecewise str aight segments, the problem can be treated in a four-dimensional phase space. For sufficiently low and high stresses the activation path can be identified directly. For intermediate stresses a more sophisticate d treatment is necessary. For numerical evaluation, the material param eters of Ni3Al are used. It turns out that the saddle-point energy is far beyond the regime to allow homogeneous thermal activation.