Appearance of an antiphase domain structure with long period in plastically deformed Ni₃Al_0·8Mn_0·2

Abstract

Neutron diffraction measurements have been carried out on an Ni₃Al_0·8Mn_0·2 alloy at different degrees of cold-working. The Mn atoms occupy the Al sublattice in the L1₂-type Ni₃Al structure. In the plastically deformed state, however, a long-period superstructure with a modulation of the lattice spacing appears. The superstructure can be taken as being composed of antiphase domains, where the alignment direction of the domains is parallel to the 〈111〉 axis of the cubic L1₂-type cell and a step shift occurs in close-packed planes. This structure remains even after annealing at 573 K for 15 h. Only small magnetic contributions to the diffraction patterns are observed.