In-situ TEM observation of loop evolution in Mo-5Re alloy under Fe⁺ irradiation

The loop evolution in Mo-5 wt.%Re alloy was studied by in-situ TEM observation under 400 keV Fe⁺ irradiation at 700 °C and 800 °C. Loop initiation always existed during the whole irradiation process. The gradual disappearance of dislocation line to grain boundary and the change of loop habit plane from [101] to [211] were in-situ observed, and the changed loop acting as an intermediate bridge led to the merging of three loops. Three main ways causing loop disappearance including the aggregation between loops, the absorption by strong defect sinks and the influence of surrounding loops were obtained from in-situ experiment. With the increase of irradiation dose, many loops formed in coarse grains but few in nanocrystals, and the areal density of dislocation lines almost kept stable in the grain with many pre-existing dislocation lines. The variation trends and relationships of the average size and volume number density of loops with irradiation temperature, irradiation dose and sample thickness were obtained. At the same irradiation temperature, the thicker the thickness of TEM foil was, the higher the yield strength increasement would be. Meanwhile, for the same sample thickness, higher temperature would reduce the irradiation hardening effect. The in-situ observation of microstructure evolution will be helpful to deeply understand the irradiation damage behavior of Mo-Re alloy.