Two-dimensional lattice image of the Mg-base Friauf-Laves phase and a new type of defect

Two-dimensional lattice images have been obtained for the two-, four-, and nine-layer type structures of the Friauf-Laves phase, Mg(Cu_0.535Al_0.465)₂. An intimate correlation is established between the lattice image and the crystal structure. With this relation, layer sequences of disordered stacking regions are determined. A new type of linear defect is found in the images and a structural model of the defect is proposed. The defect is always accompanied by a stacking fault, which is different from the usual stacking faults observed in close-packed structures.