Abstract
Cross-slip of screw superlattice dislocations in long range ordered alloys is investigated by using the weak-beam darkfield imaging method. A Ni 3(Al,Ti) alloy and Ni 3Fe were selected. The former alloy belongs to the category whose representatives are ordered up to the melting temperature; the latter alloy has an order/disorder transition at 503°C. Ni 3(Al,Ti) exhibits an anomalous increase of the yield stress with increasing temperature. Cross slip of screw superlattice dislocations onto cube planes is a characteristic feature which was found to occur with high frequency at the temperature of the onset of the anomaly. Screws dissociated on cube planes are predominantly observed. In the temperature regime below where the flow stress slightly decreases with increasing temperature octahedral cross-slip was found. In Ni 3Fe there is almost no temperature dependence of the flow stress. Octahedral cross-slip is frequently observed but cube cross-slip is rarely found. The edge superlattice dislocations are fourfold dissociated.
Published Version
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