The yield stress anomaly in Fe[sbnd]A1 alloys: The local climb lock model

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Abstract
Fe[sbnd]A1 alloys show an anomalous peak in yield stress at an intermediate temperature, as superdislocations of 1111 Burgers vector are replaced by dislocations of Burgers vector 1100. The origin of this change is shown to be the locking of the superdislocations by the climb of the partials into a non-glissile configuration by a process of local climb involving point-defect exchange between the partials. Such local climb can occur at temperatures lower than those required for general dislocation climb. A detailed examination of the characteristics of the local climb-locking process allows an evaluation of the influence of external stresses and their orientation, of the strain rate of testing and of alloy composition on the locking process and hence on the temperature where the stress peak and the change in Burgers vector occurs. These predictions are supported by the available experimental evidence on Fe[sbnd]A1 alloys for the complete range of alloy compositions.