Effect of dynamic strain-aging on mechanical and fracture properties of ferritic steels

The influence of impurities such as copper, nickel and phosphorus on radiation sensitivity of nuclear pressure vessel steels is well recognized resulting in modern presure vessel steels with reduced amounts of these trace impurities ( Steele 1983 , Murty 1985 ). While the effect of Cu content on radiation induced transition temperature is well established the mechanism by which these changes occur is at best speculative, emphasizing the lack of and the need for studies on the basic mechanism of defect-impurity interactions in these materials ( Murty 1985 ). The major objective of this study has been to characterize the influence of interstitial impurities such as carbon and nitrogen on mechanical and fracture properties of ferritic steels in the upper shelf region. The approach consists of characterizing these effects in three types of ferritic steels: a low carbon mild steel, a commercial grade 1040 steel and a nuclear grade (A 533B) pressure vessel steel. A variety of tests including simple tensile tests, impression tests ( Yu et al. 1985 ), three point slow bend tests and single specimen unloading compliance J evaluation tests have been performed on the steels. The results in mild steel and A533B steel have been recently published by Murty (1985) and by Jung and Murty (1986) and thus the results on 1040 steel will be emphasized.