A diffraction study of the substructure in cold-worked Ni3Al

A study of the substructure in cold-worked Ni3Al (Ll2) phase was performed employing x-ray powder diffraction technique. Analyses of the peak shapes, positions, and intensities of the fundamental and superstructure reflections show the importance of several substructural features, including especially the a/6 {211} {111}-type single-layer and multilayer stacking faults following deformation at the liquid-nitrogen temperature. Atomic disorder and antiphase boundaries on {111} and {100} also occur in the cold-worked material; however, these are not as prominent as those reported in the Cu-based L12 phases under comparable or less severe deformation conditions. An attempt to determine the importance of the low-energy a/3 〈211〉 {111}-type stacking fault on the basis of the limited number of superstructure reflections available in the powder pattern shows it to be less significant in the low-temperature-deformed material compared to the usual a/6 〈211〉 {111}-type intrinsic fault, although the latter has a higher energy in the Ll2 structure.