Tensile Properties of Neutron Irradiated Cr-Mn Austenitic Stainless Steel

AUSTENITIC STAINLESS STEELS IN WHICH NICKEL IS SUBSTITUTED BY MANGANESE, ARE CURRENTLY UNDER STUDY AS FUSION REACTOR STRUCTURAL MATERIALS BECAUSE THEY OFFER THE ADVANTAGE OF LOWER LONG TERM ACTIVATION COMPARED TO CR-NI STEELS. IN ORDER TO ASSESS THE MECHANICAL BEHAVIOUR OF THE CR-MN STEELS UNDER NEUTRON IRRADIA- TION, TENSILE SAMPLES HAVE BEEN IRRADIATED IN A CENTRAL CORE POSITION OF THE HFRPETTEN AT TEMPERATURE OF 300, 450 AND 550 DEGREES C UP TO THREE DIFFERENT FLUEN-CES, NAMELY 1, 5 AND 10 DPA. THE IRRADIATION TOOK PLACE IN A TRIO CAPSULE. THE SAMPLES WERE CONTAINED IN HELIUM FILLED CLODES TUBES EMBEDDED IN LIQUID NA. DIF-FERENT ALLOYS OF CR-MN STEELS HAVE BEEN INVESTIGATED. TWO HAVE A FULLY AUSTENI-TIC STRUCTURE, ONE OF THE TWO HAVING 1.5 % MO ADDITION. THE THIRD ALLOY STU- DIED HAS A HIGHER CR AND MN CONTENT AND A VERY LOW CARBON AND NITROGEN CONTENT. POST-IRRADIATION TENSILE TESTING HAS BEEN CARRIED OUT AT THE IRRADIATION TEMPE- RATURE AND AT ROOM TEMPERATURE, WITH THE SAME STRAIN RATE IN ALL EXPERIMENTS, I.E. 10-3 SEC-1. ALL TESTS HAVE BEEN CONDUCTED IN AIR. EXPERIMENTAL RESULTS SHOW THAT AT INCREASING TESTING TEMPERATURE, THE STRENGTH AND DUCTILITY OF THE CR-MN STEELS ARE DECREASING. IN COMPARISON WITH UNIRRADIATED MATERIAL, THE UNI-FORM ELONGATION OF THESE STEELS IS MORE REDUCED BY NEUTRON IRRADIATION AT THE HIGHEST IRRADIATION TEMPERATURE WHEN SPECIMENS ARE TESTED AT THE SAME TEMPERATU-RE. THE ALLOY HAVING HIGHER CR AND MN CONTENT AND VERY LOW CARBON AND NITROGEN CONTENT SEEMS TO BE MORE AFFECTED BY NEUTRON IRRADIATIONNA-NOT AVAILABL