A WEAK-BEAM STUDY OF THE DISLOCATION-STRUCTURE IN DIRECTIONALLY SOLIDIFIED NI3AL DURING DEFORMATION

The dislocation structure of a directionally solidified Ni3Al alloy de formed in tension in [001] orientation was studied using the weak beam transmission electron microscopy technique. At temperatures below the peak in flow stress, the results suggest that deformation occurs prim arily by slip of non-screw superdislocations on {111} planes, which is consistent with the widely accepted cross-slip pinning model. Above t he peak temperature, the decrease in the flow stress is attested to be the result of cross-slip of Kear-Wilsdorf locks from {010} onto {111} planes.