オーステナイト系ステンレス鋼における結晶粒微細化強化の炭素および窒素濃度依存性

The effects of C and N on solid solution strengthening and grain refinement strengthening were quantitatively evaluated using various austenitic stainless steels in which C and N were added independently to Fe-18 mass%Cr-12 mass%Ni alloys. As a result of evaluating the amount of solid solution strengthening from the intercept value in the Hall-Petch relationship, it was confirmed that N has a stronger solid solution strengthening capacity than C. On the other hand, the addition of C and N increased the slope of the Hall-Petch relationship, the so-called Hall-Petch coefficient, and the amount of grain refinement strengthening increased. Comparing the effects of C and N, there was no significant difference in the effect of increasing the Hall-Petch coefficient between the two elements at the same amount of addition. The critical grain boundary shear stress measured by nanoindentation tests and the Hall-Petch coefficient corresponded well for both steels, demonstrating that the increase in critical shear stress due to the addition of C and N results in increased grain refinement strengthening. However, the amount of grain boundary segregation was calculated to be considerably higher for C than for N, suggesting that N is more effective than C in increasing the critical grain boundary shear stress.