オーステナイト系ステンレス鋼の低サイクル疲労軟化に及ぼす炭素の影響

抄録

Effects of carbon on low cycle fatigue behavior of 20Cr-15Ni and 15Cr-15Ni stainless steels have been investigated at room temperature. Thin foils from the cyclically deformed specimens were subjected to electron microscopy. Single crystals produced by remelting some of the steels were also tested. They were deformed by compression sliced in the predetermined directions, and their dislocation configurations were observed in electron microscope. The effects of carbon and/or silicon addition on proof strength, cyclic deformation behavior and dislocation configurations were also studied. It was shown that the carbon alloyed steels showed fatigue softening as reported previously in a 0.18C-25Cr-20Ni steel. The softening was observed even at the small number of cycles, and was enhanced by an increase in carbon content and a decrease in strain amplitude. Carbon also reduced the trend of dislocations to form cellular configurations. It was revealed that such effects of carbon were increased by Si addition and that Si increased the solid solution hardening by carbon. All these results were qualitatively consist with the concept that solid solution hardening by some complexes between carbon and chromium atoms existed in the as-solution treated condition and broke down during cyclic deformation to induce fatigue softening.