Volume 18, Issue 5 (September 1990)
Dynamic Strain-Aging and Neutron Irradiation Effects on Mechanical and Fracture Properties of A533B Class 1 PV Steel and 2.25Cr-1Mo Steel
Effects of dynamic strain-aging (DSA) on upper-shelf ductility of A533B Class1 pressure vessel (PV) and 2.25Cr-1Mo steels are discussed along with those of low fluence (5 × 1021 n/m2) fast (>1 MeV) neutron irradiation on mechanical and fracture properties of the PV steel. Mechanical and fracture property data were generated using tensile and three-point bend tests. Tests were performed on as-received and irradiated A533B steel and as-received 2.25Cr-1Mo steel as a function of test temperature and applied strain-rate in the range of 300 to 623 K and 6.7 × 10−5 s−1 to 1 × 10−2 s−1, respectively. The tests were aimed at characterizing the effects of DSA on the mechanical and fracture behaviors of these steels as well as investigating the synergistic effects of DSA, and radiation defects.
Reduced ductility and fracture initiation energy were observed in both steels in the temperature and strain-rate ranges where DSA occurred. This range of temperatures corresponded to the uppershelf regime for PV steel. The strain-aging characteristics were very similar to those observed in mild steels albeit the load fluctuations and effects are relatively small. At some temperatures and strainrates, irradiation suppressed DSA resulting in improved mechanical and fracture characteristics at these relatively low fluences. Surface morphology studies performed on the fractured specimens of Cr-Mo steel revealed significant changes in the usual ductile fracture appearance at temperatures where DSA was noted.