Electron microscope image contrast from small dislocation loops. IV. Application of theoretical predictions for non-edge loops to defect analysis in irradiated molybdenum

Abstract

For pt.III see ibid., vol.9, p.2307 (1979). In part III theoretical images of small edge and non-edge dislocation loops in an isotropic BCC crystal were presented. The results demonstrated that the images from edge loops are indeed modified on going to the non-edge configuration, but that with certain exceptions the simple classification proposed for edge loops (in parts I and II) still provides a means of describing non-edge images. It was further established that several features of the images provide a powerful method of analysing the geometry of non-edge loops. Their practical application in analysing a mixed population of 1/2a(111) and a (100) vacancy loops in ion-irradiated molybdenum is explored. The results show that close agreement can be achieved between theory and experiment when the loop geometries and conditions under which the two images are obtained correspond. Further, this approach of comparing two-dimensional computer simulated images and experimental images in several diffraction vectors allows a thorough analysis of small non-edge dislocation loops.