On the contribution of nanoclusters to the irradiation-induced strengthening of metals

Experimental results are reported which are obtained from TEM studies and microhardness measurements using irradiated Mo specimens with the aim to determine the contribution from accumulations of radiation defects in the form of nanoclusters / loops to radiation hardening. The density of nanoclusters and/or dislocation loops, under conditions of retention of similarity in their size distribution, varies not only due to bombarding particle fluence change, but by way of changing energy spectrum of primary knocked-on atoms through the variation of bombarding particle mass and energy. The latter constitute fission neutrons, 50 MeV α-particles and 30 MeV protons. On the basis of the results obtained it is assumed that radiation hardening in the material studied manifests itself not as much in the difficulties of dislocation sliding over obstacles in the form of radiation defect accumulations, as in the difficulties associated with their generation. The problem of radiation hardening should be solved with taking into account the formation of Cottrell atmospheres at dislocations due to radiation defects absorption at dislocations and blocking them as Frank-Read dislocation sources