32%Mn非磁性鋼の低サイクル疲労挙動に及ぼすC,Nの影響

抄録

The effects of carbon and nitrogen on the low cyclic deformation behavior of high manganese nonmagnetic steels have been investigated at a constant total strain amplitude ranging from 0.8 × 10^-2 to 2.0 × 10^-2 in ambient air by using 32% manganese steels containing up to 0.3% carbon and to 0.3% nitrogen. The trend toward fatigue softening in the steels was generally smaller than that of austenitic stainless steels, and the steels with a very low nitrogen content showed a saturation state of stress amplitude response exhibiting no fatigue softening after initial fatigue hardening, whereas the steel strengthened by the addition of 0.3% nitrogen showed remarkable softening from the early stage of the cyclic deformation. Even in the steel containing 0.3% nitrogen, an increase in strain amplitude decreased the degree of the softening and produced the saturation state. Dislocations configuration tends to be planar in the specimens showing the softening and cellular in the specimens showing the saturation state. The softening and the associated planar dislocations configuration could be qualitatively interpreted by assuming the existence of solid solution strengthening by some complexes between interstitial and substitutional atoms and the breakdown of the complexes during the cyclic deformation.