Effect of dynamic strain aging on mechanical and fracture properties of A516Gr70 steel

The effects of dynamic strain aging (DSA) on mechanical and fracture characteristics were investigated in a ferritic steel type A516Gr70 commonly used for reactor support steels and pressure vessels. Tensile and 3-point bend tests were performed on miniature tensile and subsize Charpy specimens at various temperatures from ambient to about 700 K with specific purpose of delineating the friction and source hardening terms, and the effects of DSA on them. The total energy to fracture obtained from the areas under the load-displacement curves of 3-point bend tests of subsize Charpy specimens revealed dips in the DSA range. Unloading compliance J(IC) tests were performed on ITCT specimens at varied temperatures from 243 (-30) to about 773 K (500 degrees C) using a clip gauge (T < 400 K) and a high-temperature extensometer. At temperatures higher than 273 K valid J(IC) measurements could be made and J(IC) decreased with increasing temperature. However, no dips in the DSA range were noted contrary to the earlier observations in A533B steel and pure iron. Effect of neutron radiation exposure was investigated on the mechanical properties using subsize tensile and 3-point bend specimens. Synergistic effects of interstitial impurities and radiation-induced defects resulted in shifting the region of DSA to higher temperatures revealing improved ductility in some temperature regimes following radiation exposure. (C) 2000 Elsevier Science Ltd. All rights reserved.