THE TENSILE AND FATIGUE PROPERTIES OF TYPE-1.4914 FERRITIC STEEL FOR FUSION-REACTOR APPLICATIONS

Results of the preirradiation tensile and low cycle fatigue (LCF) tests done in specimens from the MANET cast of the 1.4914 martensitic steel are presented. The tests were performed on the subsize, thin wall specimens designed for irradiation in the PIREX facility at the Paul Scherrer Institute (PSI). Both tensile and LCF tests were performed in vacuum, in the temperature range from 300 to 870 K (720 K in the case of the fatigue tests) and are shown to compare well with results in bulk specimens. The tensile tests show a minimum in ductility at around 620 K and indicate the presence of dynamic strain ageing. The LCF tests are performed in thin wall (0.34 mm thickness) tubular specimens. Dynamic cyclic softening was observed for all fatigue testing conditions. Observations in the electron microscope show that the initial martensite lath structure is gradually replaced during cyclic life by dislocation cells. The observed cell size is inversely proportional to the square of the saturation stress.