On the relation between irradiation induced changes in the master curve reference temperature shift and changes in strain hardened flow stress

摘要

Irradiation hardening produces increases in the cleavage transition fracture toughness reference temperature (A TO). It is traditional to relate Delta T-0 to the corresponding changes in the yield stress, Delta sigma(y), as C-0 = Delta T-0/Delta sigma(y). However, it is a strain hardened flow stress, sigma(fl), in the fracture process zone that controls cleavage, rather than ay. Thus irradiation induced decreases in the strain hardening Delta sigma(sh) (< 0) Must be considered along with Delta sigma(y), (> 0) in evaluating A To. The Delta sigma(sh),h in reactor pressure vessel (RPV) steels irradiated to low doses at around 300 degrees C are small, even for large Delta sigma(y). However, the Aust, are much greater for high dose irradiations of tempered martensitic steels (TMS) that are candidates for fusion applications. As a result, for the TMS case, the C-0 are less, and in some instances much less, than for RPV steels and irradiation conditions. We address two key questions. First, how does Delta sigma(sh) influence the C-0 = Delta T-0/Delta sigma(y), relation? Second, is it possible to derive a universal relation between Delta T-0 and Delta sigma(fl) averaged over a pertinent range of e, , such that a C0, = Delta T-0/ is independent of the individual values of Delta sigma(y) and Delta sigma(sh)? The results of this study suggest that averaged between 0 and 0.1 provides a similar C0, for various assumptions about the effect of irradiation on Delta sigma(sh). Notably, changes in indentation hardness, Delta H, are also directly related to this same . Hence, measurements of Delta H should provide a good basis for assessing Delta T-0 for a wide range of alloys and irradiation conditions. (c) 2007 Published by Elsevier B.V.