Regulating the dislocation-nanocluster interactions by electrical pulses to alleviate material hardening

Abstract

The life of the reactor pressure vessels (RPV) is limited because of the radiation-induced defects in the matrix, such as nanoclusters and dislocation loops, which cause material hardening (i.e., irradiation embrittlement) by impeding the free dislocation movement. The conventional life extension treatment mainly restores the performance of degraded RPVs by dissolving nanoclusters at high temperatures above 430 °C. This study found that even without dissolving Cu-rich nanoclusters, electric pulse treatment at a lower processing temperature (150 °C) can still alleviate material hardening and eliminate discontinuous yield behavior. The influence of non-thermal effects such as electron wind force and electric field on the interaction between dislocations and nanoclusters under pulse electric field was discussed through molecular dynamics simulation. The results indicate that due to the reduction of critical pinning stress, dislocations are more likely to attract and cut nanoclusters. Correspondingly, under the lower pinning effect of nanoclusters, the dislocation density was effectively reduced by 16%, and some entangled dislocations were transformed into discrete states. Therefore, different from traditional annealing treatments that directly eliminate nanoclusters at high temperatures, this electric pulse processing technology alleviates material hardening by regulating the interaction between dislocations and nanoclusters, which provides a new path for “in situ” extending the service life of RPVs at low temperatures.