TEM observations of superlattice intrinsic stacking faults in polycrystalline Ni_74.5Pd₂Al_23.5

Dislocations consisting of two super-Shockley partials bounding superlattice intrinsic stacking faults (SISFs) in Ni_74.5 Pd₂Al_23.5 produced by compressive deformation at room temperature were observed by transmission electron microscopy. The results show that the majority of the faults are truncated loops, i.e., the partials bounding the SISFs have the same Burgers vector, and the SISFs are generated from APB-coupled dislocations, according to a mechanism proposed by Suzuki et al. and recently modified by Chiba and Kanada. The addition of Pd has no similar effect on SISFs in Ni₃Al as boron doping. No connection between SISF density and ductility can be found in this alloy.