Dislocation dissociation in cubic Al3Ti alloys

Publisher Website
Google Scholar
Abstract
Recently there have been conflicting reports concerning the dissociation scheme of superdislocations in Al3Ti alloyed to the cubic structure. This discrepancy can perhaps be explained by the difficulty of applying invisibility criteria for dislocations imaged under weak beam electron microscope conditions. The present study examines dissociated dislocations under a wide range of imaging conditions to deduce that dissociation by the creation of an antiphase boundary (APB) fault is the scheme operating, at room temperature as well as at high temperature. At the triple-point nodes of intersecting dislocations there are localized regions of superlattice intrinsic stacking faults (SISFs), which allow an estimation of SISF energy for comparison with the APB fault energy. This comparison confirms that dissociation by the creation of an APB fault should be the preferred scheme. After high-temperature deformation many of the superdislocations have their APB on cube planes and remain mobile with no evidence of dislocation locking. Such observations, some made on materials showing anomalous strengthening and others on materials not showing this anomaly, confirm that Kear-Wilsdorf locking is not the cause of the anomalous strengthening sometimes found for these materials.