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

The effects of dynamic strain aging (DSA) on mechanical and fracture charac teristics 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 v arious temperatures from ambient to about 700 K with specific purpose of de lineating the friction and source hardening terms, and the effects of DSA o n them. The total energy to fracture obtained from the areas under the load -displacement curves of 3-point bend tests of subsize Charpy specimens reve aled 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 ga uge (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 contr ary to the earlier observations in A533B steel and pure iron. Effect of neutron radiation exposure was investigated on the mechanical pro perties using subsize tensile and 3-point bend specimens. Synergistic effec ts of interstitial impurities and radiation-induced defects resulted in shi fting the region of DSA to higher temperatures revealing improved ductility in some temperature regimes following radiation exposure. (C) 2000 Elsevie r Science Ltd. All rights reserved.