Study of atomic displacement fields in shape memory alloys by high-resolution electron microscopy

The distortion of the atomic lattice is determined using a recently developed method of analysing high resolution electron microscope images. The analysis is carried out in terms of the individual lattice fringes which contribute to the image contrast. A perfect set of fringes has an amplitude and phase given by the corresponding Fourier component. A distorted lattice can be analysed by introducing the concept of a ‘local’ Fourier component, representing the local values of amplitude and phase as a function in position of the image. The local phase is used to determine the line of a perfectly coherent interface between two sets of lattice planes. The degree of self-accommodation of a series of martensitic plates in a Cu–Zn–Al shape-memory-alloy is studied by the phase analysis of an experimental high resolution image.