Yield stress anomalies in ordered alloys: a review of microstructural findings and related hypotheses

In intermetallic alloys, the mechanical properties accompanying the yield stress anomaly show a large variety of facets that may differ from one family of alloys to the next. A condition generally fulfilled for a yield stress anomaly to take place is that the exhaustion rate competes strongly with the multiplication rate of mobile dislocations. There are, however, a number of differences as to the origin of exhaustion, that is, of the mechanism(s) for dislocation locking. This may indeed take place by transformation of a dislocation core by cross-slip, a well-known and quite commonly encountered example is that of Kear–Wilsdorf (KW) locks in various ordered structures. An alternative out-of-plane core structure is that of climb-dissociated dislocations. There are in addition situations where the dislocation core does not have the potential towards forming sessile configurations yet the alloy may behave anomaloulsy.