放電プラズマ焼結により作製したCrMnFeCoNi合金の疲労き裂伝ぱ特性に及ぼす結晶粒径の影響

抄録

In this study, in order to investigate the effect of grain size on fatigue crack propagation in CrMnFeCoNi high-entropy alloy (HEA) fabricated by spark plasma sintering, stress intensity factor-K decreasing tests were conducted under the force ratios from 0.1 to 0.8 in ambient condition. Crack profiles were observed by scanning electron microscopy, and microstructures around crack profiles were analyzed by electron backscatter diffraction. Threshold stress intensity factor ranges ΔK_th in HEA tended to decrease with increasing the force ratio and decreasing grain size. Effective threshold stress intensity factor ranges ΔK_eff,th were lower than ΔK_th and almost the same value regardless of the force ratio and grain size. The fatigue crack path in the coarse-grained structure was more tortuous than that of fine-grained structure. The effect of grain size on fatigue thresholds in CrMnFeCoNi alloy was disappeared by eliminating the crack closure phenomenon.