An in situ sem kossel x-ray diffraction study of pseudoelasticity

Abstract

The coming of age of “smart” materials and structures, i.e. of materials and structures capable of sensing and acting upon changes in the surroundings, has prompted a resurgence of interest in elastic martensites. Here, we have used a miniature ball and ring deformation rig to study the nature of pseudoelastic behavior of a CuAlNi alloy single crystal. By photographing changes in the Kossel X-ray diffraction pattern from a deforming disc of this crystal and, in particular, by recording the pattern when line broadening arising from elastic strain is just sufficient to prevent resolution of the CuK α1/K β doublet, we have been able to estimate the level of local strain at which phase transformation occurs. Analysis of the breaking up, prior to this, of a point of triple intersection between sharp diffraction lines has permitted determination of a crystal structure, precursor to that for the low temperature phase.