Effect of dynamic strain aging on the microstructure and mechanical properties of a reactor pressure vessel steel

Analysis of the dynamic strain aging (DSA) effect was carried out for a reactor pressure vessel (RPV) steel, the A508-class3. The aging process includes the application of various plastic strain values of 1%, 2%, 4%, 6% and 8% with different strain rates at certain tempering temperatures. The microstructure of the specimens was analyzed in detail using optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that serrated stress-strain curves occurred at the DSA process, and the new hardening phase of M23C6 type carbide is precipitated to pin the mobile dislocations. The hardening effect increases with the increase of the strain value within the uniform plastic strain region, even though the softening effect caused by dynamic recovery is obvious. After analyzing the correlations between aging parameters, hardening, ductile-brittle transition temperature and irradiation effect, it is found that the degeneration of mechanical properties caused by DSA is similar to the irradiation effect.