Temperature dependence of irradiation hardening due to dislocation loops and precipitates in RPV steels and model alloys

TL;DR

This study investigates how irradiation hardening in RPV steels varies with temperature, focusing on dislocation loops and precipitates, and explains discrepancies between different testing methods through a thermally activated dislocation motion model.

Contribution

It provides a comparative analysis of irradiation hardening contributions in RPV steels and model alloys across different temperatures, incorporating TEM, mechanical testing, and atomistic simulations.

Findings

Pinning strength factors are lower in RPV steels than in model alloys.

Discrepancies are explained by a thermally activated dislocation motion model.

Temperature and strain rate differences affect hardening measurements.

Abstract

A relative contribution to irradiation hardening caused by dislocation loops and solute-rich precipitates is established for RPV steels of WWER-440 and WWER-1000 reactors, based on TEM measurements and mechanical testing at reactor operating temperature of 563 K. The pinning strength factors evaluated for loops and precipitates are shown to be much lower than those obtained for model alloys based on the room temperature testing as well as those evaluated by means of atomistic simulations in the temperature range of 300 to 600 K. This discrepancy is explained in the framework of a model of thermally activated dislocation motion, which takes into account the difference in temperature and strain rate employed in atomistic simulations and in mechanical testing.