| 摘要 |
PROBLEM TO BE SOLVED: To remarkably improve the fatigue strength of the steel material by controlling the effective components in the fatigue crack propagating lower threshhold value to the value equal to or above the specified one by the exis tence of an atomic pair of an interstitial element and a substitutional element confirmed by AP-FIM analysis. SOLUTION: In the case SUS316 austenitic stainless steel is added with N as an interstitial element by >=0.2 mass %, its fatigue crack propagating characteristics including theΔKeff,th improve by >=50%. From the result of AP-FIM analysis, it is found that such improvement of the fatigue characteristics is done by a pair of N as an interstitial element and Mo as a substitutional element. In this way, the effective componentsΔKeff,th in the fatigue crack propagating lower threshhold value improve more than MPa.m0.5 by >=20%. The atomic pair of the interstitial element and the substitutional element can be formed by adding respective elements in the case of the steel is subjected to refining or the like, and the addition of these elements and the control of the ratios are easily executed by AP-FIM analysis.
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