Effect of Strengthening Methods on the Defect Evolution under Irradiations Investigated with Rate Theory Simulations

Abstract

Under irradiations, mechanical performance of nuclear alloys would degrade due to irradiation induced defects. Different strengthening methods can play a different role in the evolution of the defects. In this study, the effect of four typical strengthening methods including fine grain strengthening, dislocation strengthening, second phase strengthening and solid solutions strengthening on the defect evolutions in bcc iron-based alloys are investigated with rate theory simulations, a technique capable of simulating a long-term evolution of defects caused by irradiations. Simulations show that at high dose, irradiation induced voids become the dominating factor that affect irradiation hardening. Strengthening methods with the enhancement of sink strength (fine grain strengthening, dislocation strengthening and second phase strengthening) have little effects on the evolution of voids, while strengthening method with impediment of migration of defects (solid solutions strengthening) can effectively inhibit the nucleation and growth of voids. For fine grain strengthening and dislocation strengthening, the irradiation hardening is almost kept unchanged when changing grain size and initial dislocation density. For second phase strengthening, the irradiation hardening can be inhibited to some extent by increasing mainly the number density of precipitates. The solid solutions strengthening is the most proper method to inhibit irradiation hardening of bcc iron-based alloy because it can inhibit the development of voids, especially at high dose.