Effect of neutron irradiation on the dynamic fracture toughness behavior of the 12% Cr steel MANET-I investigated using subsize V-notch specimens

Abstract

The effect of neutron irradiation on the dynamic fracture toughness behaviour of the 12% Cr steel MANET-I was investigated using DIN 50115-KLST, subsize, V-notch impact bend specimens (3 × 4 × 27 mm 3). The microstructure of the steel was varied by employing different quenching and austenizing conditions. The specimens were irradiated in the HFR Petten at 300, 400, and 475°C to displacement damage levels as high as 5 dpa NRT. Experimental results are reported from an ongoing program aimed at determining the influence of irradiation-induced microstructural changes on the impact properties of MANET-I: the ductile-to-brittle transition temperature (DBTT), the relative fracture toughness, and the dynamic plane strain fracture toughness. Following irradiation a large increase in the DBTT and a remarkable decrease in the upper-shelf energy (USE) were observed. The changes in the properties depend strongly on the irradiation temperature. The DBTT and USE of the irradiated specimens also depend clearly on the initial microstructure of the material. The increase in DBTT and the decrease in USE are in general greater at 300 than at 400 and 475°C. Under proper conditions the instrumented impact test can be used to determine the dynamic plane strain fracture toughness K 1 d and the J-integral of unirradiated and irradiated materials.