On the basis of experiments which had been performed on polycrystalline samples of the  phase, a statistical model was proposed in order to account for the stress anomalies which were observed in this material at intermediate temperatures. The statistical analysis was based upon a particular mechanism, in which dislocations were successively pinned on localized intrinsic obstacles and were unzipped via the lateral motion of cusps. Due to an increase in pinning-point density with increasing temperature, the probability of operation of the unzipping mechanism was shown to depart from unity above a critical temperature. The resultant strong exhaustion mechanism of mobile dislocations naturally yielded a stress anomaly. The model also accounted for other characteristic features in this temperature range, such as the high work-hardening rate and the very low strain-rate sensitivity.

F.Louchet, B.Viguier: Philosophical Magazine A, 1995, 71[6], 1313-33