Formation of dislocation channels in neutron irradiated molybdenum

The formation of deformation-induced dislocation channels in neutron irradiated molybdenum and the loop-dislocation interactions were investigated using transmission electron microscopy. It is suggested that the irradiation-induced defect - microstructure is unstable with respect to the stress. Under the influence of the stress, loops start gliding on their glide cylinders in transition region of a cascade where vacancies and interstitials may coexist. Results indicate that loop-loop interactions have a significant role in the early stage of channel formation; dislocations are not seen either within or at the ends of the embryonic channels. There are two consequences of loop-loop interactions: the reduction in the loop density due to their mutual annihilation in localized regions and the increase in the loop sizes due to the coalescence of loops having the same nature. On further stressing, the segments of the larger loops could serve as the source of mobile dislocations. The yielding may occur when the stress level is high enough to activate the coalescence-produced glide sources. Furthermore, results on the attractive loop-dislocation interactions suggest that they may not have a significant role in eliminating defect clusters. On the other hand, the repulsive interactions may have a substantial role in altering the microstructure of the irradiated metals. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.