Effect of Ferrite Grain Boundary on Strain Aging Behavior in Nb-Bearing Ultra-Low-Carbon Steel Sheets

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Abstract:

Effect of grain boundary on strain ageing behaviour of Nb-bearing ULC steel sheets has been studied at the aging temperature from 70 to 220°C, using 2% pre-strained specimens with different ferrite grain sizes of 9.5μm and 183μm. Two different hardening stages were exhibited in the fine-grain specimen, whereas only a single hardening stage was shown in the large-grain specimen. The increase in YP of the first hardening stage was around 30MPa; the activation energy of this stage was estimated to be from 83 to 86kJ/mol, which is close to that of body diffusion of carbon atoms in α-Fe. The increase in YP of the second hardening stage reached 90MPa; the activation energy was 135kJ/mol, which is close to that of body diffusion of Fe atoms in grain boundary and precipitation of η-carbide. From TEM observations and nanoindentation analyses, it was inferred that the dominant mechanism could be dislocation pinning by carbon atoms for the first hardening stage, and grain boundary hardening or hardening around it for the second.

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Materials Science Forum (Volumes 706-709)

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2222-2227

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January 2012

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[1] A. H. Cottrell and B. A. Bilby: Proc. Phys. Soc., A62(1984), p.49.

Google Scholar

[2] S. Harper: Phys. Rev., 83(1951), p.709.

Google Scholar

[3] S. Hanai, N. Takemoto, Y. Tokunaga and Y. Mizuyama: Trans. ISIJ, 24(1984), p.17.

Google Scholar

[4] A. K. De, S. Vandeputte and B. C. DeCooman: J. Mater. Eng. Perform., 10(2001), p.567.

Google Scholar

[5] D. V. Wilson and B. Russel: Acta Metall., 8(1960), p.468.

Google Scholar

[6] A. K. De, S. Vandeputte and B. C. DeCooman: Scripta Mater., 44(2001), p.695.

Google Scholar

[7] N. Maruyama and M. takahashi: Tetsu-to-Hagane, 93(2007), p.32.

Google Scholar

[8] D. V. Wilson: Metal Science Journal, 1(1967), p.40.

Google Scholar

[9] K. Takeda, N. Nakada, T. Tsuchiyama and S. Takaki: ISIJ Int., 48(2008), p.1122.

Google Scholar

[10] D. V. Wilson and B. R. Russell: Acta Metall., 8(1960), p.36.

Google Scholar

[11] A. Okamoto, H. Takahashi and T. Hino: Trans. ISIJ, 21(1981), p.1802.

Google Scholar

[12] M. Kinoshita and A. Nishimoto: CAMP-ISIJ, 3(1990), p.1780.

Google Scholar

[13] C. Wert: Phys. Rev., 79(1950), p.601.

Google Scholar

[14] M. Cohen: Trans. JIM, 11(1970), p.145.

Google Scholar

[15] D. W. James and G. M. Leak : Phil. Mag., 14(1966), p.701.

Google Scholar

[16] R. H. Doremus: Trans. Met. Soc. AIME, 218(1960), p.596.

Google Scholar

[17] T. Waterschoot, K. Verbeken and B. C. DeCooman: ISIJ Int., 46 (2006), p.138.

Google Scholar

[18] J. D. Baird: Iron and Steel, 36(1963), p.186.

Google Scholar

[19] H. Abe: Scandinavian Journal of Metallurgy, 13(1984), p.226.

Google Scholar