Electron microscope image contrast from small dislocation loops. II. Application of theoretical predictions to defect analysis in irradiated metals

For pt.I see ibid., no.7, p.1359 (1977). Previously the authors presented theoretical images of small, edge dislocation loops in an isotropic BCC crystal. The results demonstrated the wide range of image contrast that is obtained as a function of loop geometry and location in the crystal and diffracting conditions. In the case of loops located within the layer structure, it was shown that image symmetry is a sensitive function of modulus g.b and loop orientation. Image contrast was classified into four basic types corresponding to (1) mod g.b mod =0 (loops inclined), (2) mod g.b mod =0 (loops approximately edge on), (3) mod g.b mod 3. The authors now explore the practical usefulness of this approach to the determination of Burgers vector directions of small loops in irradiated molybdenum and copper crystals. More specifically, a range of examples of experimental images in these two metals have been selected for comparison with the theoretical predictions.