Neutron scattering study of the martensitic transformation in a Ni-Alβ-phase alloy

Abstract

A high-resolution neutron scattering study of ${\mathrm{Ni}}_{62.5}$ ${\mathrm{Al}}_{37.5}$ shows that the martensitic transformation is associated with a homogeneous distortion and a nearly seven-fold modulation of the cubic lattice which is predicted by an observed phonon anomaly above $T_M$. In the low-temperature 7R phase a nonuniform spacing of superlattice reflections and unusual line shapes are observed which are believed to arise from stacking faults.