Deformation and Fracture Behavior of AISI 403 Stainless Steel for Nuclear Structural Applications

Abstract

The deformation and fracture behaviour of AISI 403, a tempered martensitic stainless steel for end fitting application of Pressurised heavy water reactor is being reported. The deformation behaviour studies entailed characterisation of tensile behaviour in the temperature range 77 - 873 K for the as recieved and the fine grained Nb modified variant of AISI 403. the study of elevated tensile behaviour in the two steels has been undertaken with the purpose of characterising the strain rate - temperature domain of the occurrence of dynamic strain aging (DSA) phenomenon. In both steels, while the temperature range for the manifestations of characteristic anomalies in the tensile curve due to DSA was observed within 523 - 673K, the strain domain for the fine grained Nb modfied variety was significantly higher as comapred with the as recievied variety. The low temperature tensile tests for the as recieved AISI 403 revealed the presence of Pseudo=alloy softening in the temperature range 273 - 193 K. The effect of high DBTT of the AISI 403 steel was shown by the fracture toughness tests in the J-integral format at room temperature that displayed significant scatter in smaples with high in-plane and out of plane constraint. Smaples with lower constraint showing stable crack growth were further tested at high temperature to obtain the temperature dependence of initiation fracture toughness and propagation touhgness. Within the DSA tempertaures a sharp decline in the fracture properties were observed. A mechanistic interpretation for the manifestations of the various observed phenomena is presented.