An in-situ experiment in an electron microscope is now a well established and useful technique in materials science. In this review recent contributions of in-situ experiments, especially of straining and heating experiments, to materials science will be high-lighted.The earlier works have been reviewed by Saka and Imura.It is believed that an external stress gives rise to an anistropy in the rate at which point defects are absorbed by edge dislocations; this mechanism is considered to explain the irradiation creep. A combined in situ tensile/irradiation experiment in a HVEM has been carried out to study effects of applied stress on the growth of dislocation loops. Fig. 1 shows typical microstructures of Ag irradiated at 403K for 10 min with 1MV electrons in the absence (a), and in the presence of an external stress of 5.5 kg/mm2 (b). Frank loops of interstial type, formed by electron irradiation, grew more rapidly in the direction of the external tensile stress than in the others. These results show that an external tensile stress has a profound effect on climb rates of Frank loops of interstitial type. However, detailed analysis of the results indicates that there is a considerable discrepancy between experiment and theory.
Formation and Growth Process of Dislocation Loops in Zircaloys under Electron Irradiation
