On the characterization of basal plane stacking faults in N9R and N18R martensites

Abstract

Theory of diffraction from 9R martensites containing sequence and deformation type faults is developed. It is shown that a distinction can be made between the sequence and deformation faults by analysing diffuse streaks on the diffraction patterns obtained from such crystals. Further, a distinction amongst the three sequence faults themselves on the one hand and the two deformation faults on the other hand is also shown to be possible. Such distinctions are not possible for the N9R or N18R structures using the g · R criterion of the conventional transmission electron microscopy. From a comparison of the theoretically predicted diffraction effects with those experimentally observed by earlier workers, it is concluded that the faults present in the N9R martensites are of predominantly sequence type. The theory developed for N9R is also applicable to N18R structure for the reciprocal lattice rows common with the fundamental structure.