Fieldion microscopy of frank loops in platinum: Computer simulation and experimental observation

Abstract Small dislocation loops are difficult to interpret by availablo experimental means. However. Frank loops may be confidently imaged and their nature interpreted unambiguously with the field-ionmicroscope. A reformulation of the displacement equations for a pure edge dislocation into cylindrical coordinates permits the writing of a closed expression for an entire dislocation loop which is then employed to give computer-simulated field-ion patterns of several extrinsic and intrinsic loops. The simulated images are compared with experimental images of quenched and annealed platinum and clearly show intrinsic Frank loops to be present. A general procedure is described that permits the differentiation between intrinsic and extrinsic Frank loops in any part of the field-ion image and distinguishes these from other possible defects.