Effect of temperature on dislocation loop evolution in RPV model steel: In-situ Fe+ irradiation

To better understand the evolution of dislocation loops in RPV steel at different temperatures, in-situ irradiation experiments of 400 keV Fe⁺were conducted using a RPV model alloy Fe–1.0Mn–0.7Ni–0.2Si (wt.%) at 240 °C, 350 °C, 450 °C, and 550 °C. The nucleation rate of dislocation loops increases first and then decreases with the increase of irradiation dose when T < 550 °C. The lower the temperature, the higher the nucleation rate of dislocation loop. The relationships between the average size & number density of dislocation loops and damage dose, as well as irradiation temperatures, is analyzed. The data indicate that higher irradiation temperatures result in larger loops with lower density. This is most evident at 550 °C, where both the average size and number density of dislocation loops vary significantly. Furthermore, quantitative analysis of the proportion of ½<111> and 〈100〉 dislocation loops at different temperatures reveals that when the temperature increases from 450 °C to 550 °C, the proportion of 〈100〉 loops decreases, for example, from 42 % to 25 % at 3.0 dpa. Moreover, the irradiation hardening induced by dislocation loops generally decreases with increasing temperature. These findings offer novel insights into the irradiation damage mechanisms in RPV steel.