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| STRENGTHENING OF THE Fe-0.04Nb-0.02C ALLOY |
| Lin Dong-liang (Lin Tung-liang) (Shanghai Jiaotong University) |
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Cite this article:
Lin Dong-liang (Lin Tung-liang) (Shanghai Jiaotong University). STRENGTHENING OF THE Fe-0.04Nb-0.02C ALLOY. Acta Metall Sin, 1978, 14(4): 323-460.
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Abstract By hot roiling at temperatures between 1175—900℃ and subsequently isothermal treating at 600℃, the grain size of α-Fe was refined to 7—22μm in diameter. There were a number of 3-and 2-dimensional dislocation networks and precipitates of small NbC particles in α-Fe. The lower yield stress of the alloy can be increased up to 35—42 kg/mm~2 by the combined strenthening of grain refinement, second phase particle (NbC) and dislocation substructure. The lower yield stress σ_(1y) is related to the average value of the grain diameter by Hall-Perch equation:σ_(ly)=σ_i+k_yd~(1/2) where k_y is proportional constant of strengthening by grain refinement, k_y=2.2 kg/mm~(3/2); σ_i is friction stress on moving dislocations in grains. The values of σ_i for the specimens isothermal treated for 30 see, 40 rain and 3 hr at 600℃ are 21.5, 13.5 and 13.5 kg/mm~2 respectively.The dislocation density in the alloy is increased with increasing deformation. The relationship between the square root of average dislocation density and the flow stress can be expressed in the form of the following equation:σ_f=σ_0 +αGbρ~(1/2) where G is the shear modulus; b is the magnitude of the Burgers vector;α is the strengthening proportional constant by the interaction of dislocations, α=0.37;σ_0 is the flow stress due to all cases (e. g. grain refinement and dispersion strengthening etc. ) other than dislocation interaction. With the specimens isothermal treated at 600℃ for 30 see, 40 rain and 3hr, the values of σ_0 are found to be 34, 30 and 30 kg/mm~2 respectively. Results from the analysis of experimental data and theoretical calculations have shown that the value of σ_i is the summation of the contribution to yield stress by the dispersion strengthening of second phase particle (NbC)σ_p, dislocation substructure strengthening σ_d and lattice friction stress σ_1, i. e.σ_i=σ_p+σ_d+σ_1The "precipitate growth"dislocation loops have been observed around the NbC particles precipitated in α-Fe. The mechanisms for "precipitate growth" dislocations have been discussed in this paper, but their effect on the strengthening has not yet been clarified and will be further investigated.
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Received: 18 April 1978
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[1] Morrison, W. B. and Woodhead, J. H., J. Iron Steel Inst., London, 201 (1963) , 43．
[2] Morrison, W. B., J. Iron Steel Inst., London, 201 (1963) , 317．
[3] Gray, J. M. et al., J. Iron Steel Inst., London, 203 (1965) , 812．
[4] Gray, J. M. and Yeo, R. B. G., ASM Trans. Quart., 61 (1968) , 255．
[5] Duekworth, W. E. and Baird, J. D., J. Iron Steel Inst., London. 207 (1969) , 854．
[6] Processing and Properties of Low Carbon Steel, TMS-AIME, New York, 1973．
[7] The Proceedings of the Conference "Microalloying 75" , Washington, D. C., Sept., 1975．
[8] Lin, T. L. (林栋梁) and McLean, D., Metal Sci. J., 2 (1968) , 108．
[9] Ham, R. K., Phil. Mag., 6 (1961) , 1183．
[10] Silcock, J. M., J. Iron Steel Inst., London, 201 (1963) , 409．
[11] Duwez, P. and Odell, F., J. Electrochem.. Soc., 97 (1950) , 299．
[12] Calm. J. W. and Nutting, J., Trans. AIME, 215 (1959) , 526．
[13] Dingley, D. J. and McLean, D., Acta Met., 15 (1967) , 885．
[14] Keh, A. S. and Weissman, S., Eleetron Microscopy and Strength of Crystals, Ed. by G. Tho mas and J. Washburn, Wiley, New York, 1963, p. 231．
[15] Tekin, E. and Kelly, P. M., Precipitation from Iron-Base Alloys, Eds. by G. R. Speieh and J. B. Clark, Gordon and Breach, New York, 1963, p. 173．
[16] Manual on Electron Metallography Techniques, Amer. Soe. Test. Mater., Spec. Tech. Publ., № 547, 1973．
[17] Mondino, M. and Seeger, A., Scripta Met., 11 (1977) , 817．
[18] Orowan, E., Symposium on Internal Stresses in Metals and Alloys, Institute of Metals, London, 1948, p. 451． Dislocations in Metals, Ed. by M. Cohen, AIMME, 1954, p. 131．
[19] Ashby, M. F., Oxide Dispersion Strengthening, Ed. by G. S. Ansell, T. D. Cooper and F. V. Lenel, Gordon and Breach, New York, 1968, p. 143．
[20] Ashby, M., Z. Metallk., 55 (1964) , 5． |
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