PSI - Issue 13

Kohei Kishida et al. / Procedia Structural Integrity 13 (2018) 1032–1036 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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Therefore, the variation trend of hardness at 433 K can be explained by the carbide precipitation. In particular, the decrease in hardness is known as the over-aging effect (McGrath and Bratina, 1967). In addition, the formation of carbide decreases the content of solute carbon. The over-age-softening and reduced-DSA effect cause the degradation of the fatigue limit of the Fe-0.16C-1Si alloy. Consequently, the Si addition delays the carbide formation at 433 K, according to the degradation degree of fatigue limit upon increasing the temperature from 293 to 433 K. However, even with the addition of 1% Si, carbide was formed eventually, which causes the degradation of the fatigue limit. We investigated the effect of Si on the temperature dependence of the fatigue limit of ferritic alloys with supersaturated carbon. The following are the conclusions of the present study. 1) The addition of Si increased the fatigue limit at 293 K in Fe – C ferritic alloys owing to solution hardening. 2) The degradation of fatigue limit by dynamic precipitation at 433 K was suppressed in the Fe-0.016C-1Si alloy, compared with that of the Fe-0.017C alloy. However, carbide was formed eventually in the alloy after significant aging at 433 K, and thus, the degradation of the fatigue limit was not suppressed by Si. 3) Fatigue crack did not stop propagating in the Fe-0.016C-1Si alloy even at the fatigue limit, which is an adverse effect of the addition of Si. Acknowledgements Abbaschian, R., Reed-Hill, R.E., 2008. Physical metallurgy principles. Cengage Learning. Bain, E.C., 1940. Functions of the alloying elements in steel. American Society for Metals. Chan, K.S., Chen, L.H., Lui, T.S., 1997. Serrated Flow and Dynamic Precipitation in Elevated Temperature Tensile Deformation of Fe–Mn–Al–C Alloys. Materials Transactions, JIM 38, 420-426. Harper, S., 1951. Precipitation of Carbon and Nitrogen in Cold-Worked Alpha-Iron. Physical Review 83, 709-712. Kaneko, H., Nishizawa, T., Tamaki, K., 1963. Sulfide-forming Tendency of Alloying Elements in Steel. Journal of the Japan Institute of Metals 27, 299-304. Koyama, M., Ren, B., Yoshimura, N., Sakurada, E., Ushioda, K., Noguchi, H., 2017a. Intrinsic Factors that Trigger the Coaxing Effect in Binary Fe – C Ferritic Alloys with a Focus on Strain Aging. ISIJ International 57, 358-364. Koyama, M., Yamamura, Y., Che, R., Sawaguchi, T., Tsuzaki, K., Noguchi, H., 2017b. Comparative study on small fatigue crack propagation between Fe-30Mn-3Si-3Al and Fe-23Mn-0.5C twinning-induced plasticity steels: Aspects of non-propagation of small fatigue cracks. International Journal of Fatigue 94, Part 1, 1-5. Li, B., Koyama, M., Sakurada, E., Yoshimura, N., Ushioda, K., Noguchi, H., 2016. Potential resistance to transgranular fatigue crack growth of Fe – C alloy with a supersaturated carbon clarified through FIB micro-notching technique. International Journal of Fatigue 87, 1-5. Li, B., Koyama, M., Sakurada, E., Yoshimura, N., Ushioda, K., Noguchi, H., 2017. Underlying interstitial carbon concentration dependence of transgranular fatigue crack resistance in Fe-C ferritic steels: The kinetic effect viewpoint. International Journal of Fatigue 98, 101-110. Li, B., Koyama, M., Sakurada, E., Yoshimura, N., Ushioda, K., Noguchi, H., 2018. Temperature dependence of transgranular fatigue crack resistance in interstitial-free steel and Fe-C steels with supersaturated carbon: Effects of dynamic strain aging and dynamic precipitation. International Journal of Fatigue 110, 1-9. McGrath, J.T., Bratina, W.J., 1967. Interaction of dislocations and precipitates in quench-aged iron-carbon alloys subjected to cyclic stressing. Acta Metallurgica 15, 329-339. Oates, G., Wilson, D.V., 1964. The effects of dislocation locking and strain ageing on the fatigue limit of low-carbon steel. Acta Metallurgica 12, 21-33 Sato, T.-o., Nishizawa, T., 1955. Study on Carbides in Iron and Steel by Electrolytic Isolation (Report 2). Partition of Alloying Elements between Ferrite and Carbides. Journal of the Japan Institute of Metals 19, 385-389. Ushioda, K., Goto, S., Komatsu, Y., Hoshino, A., Takebayashi, S., 2009. Evolution of Dislocation Structure and Fatigue Crack Behavior in Fe–Si Alloys during Cyclic Bending Test. ISIJ International 49, 312-321. Wilson, D.V., Tromans, J.K., 1970. Effects of strain ageing on fatigue damage in low-carbon steel. Acta Metallurgica 18, 1197-1208. 4. Conclusions MK, KT, and HN acknowledge the financial support by JSPS KAKENHI (JP16H06365). References