LOW-TEMPERATURE FRACTURE-BEHAVIOR OF 12-PERCENT-CR-15-PERCENT-MN AUSTENITIC STEELS

The primary objective of the present study is to investigate the low temperature toughness of high Mn-Cr austenitic steels which are being developed as one candidate alloy for the structural material of fusion reactor from the point of view of reduced radio-activation. In the present work, the effects of V, Ti and P on the low temperature toughness of the alloys with the basic composition of 12%Cr-15%Mn-(0.1-0.2%)C-(0.1-0.2%)N are investigated. Coarse precipitates of M(23)C(6) on the grain boundaries caused intergranular fracture and tiny precipitates of VN within the grains enhanced cleavage fracture in aging treated alloys. The addition of Ti was beneficial for improving toughness due to the restraining of the tiny VN precipitation. The addition of P, however, deteriorated the low temperature toughness of the alloys. The toughness values of the 12%Cr-15%Mn materials were compared with those of JFMS (a modified 9Cr-2Mo ferritic stainless steel) and JPCA (modified 316 austenitic stainless steel).