采用完全淬火+两相区再加热-淬火-分配(IQ$\&$P)热处理工艺对0.23C-1.8Mn-1.35Si钢进行处理, 获得了具有亚温铁素体、马氏体以及广泛分布于原奥氏体晶界、相界等处的残余奥氏体等构成的多相组织. 利用SEM, XRD以及EBSD等对不同热处理阶段钢的微观组织进行了表征. 结果证实, 该多相组织低合金钢中残余奥氏体的获得主要依赖于以下两点: 一是两相区再加热阶段逆转变奥氏体组织中的富Mn富C, 二是淬火--分配阶段残留奥氏体在分配过程中的二次富C, 通过上述的两步元素富集处理可以使该低碳钢在室温下获得超过10%含量的残余奥氏体, 而残留奥氏体在分配过程中的二次富C则对该类钢中残余奥氏体的形成及其在室温下的稳定化起到了至关重要的作用. 由于广为分布的残余奥氏体在形变过程中的TRIP效应, 使得该类钢种在拉伸变形过程中获得了持续的加工硬化能力, 从而实现了强度与塑性的良好结合. 测试结果表明, IQ&P钢的强塑积超过了26 GPa?%, 屈服强度大于600 MPa, 抗拉强度超过900 MPa, 均匀延伸在16\%以上, 常温半厚冲击韧性达到了39 J.
The development of high performance steels needs to realize the combination of high strength, high plasticity and high toughness. Multiphase microstructure which contains a specific proportion of retained austenite is conductive to enhance the toughness and plasticity of the steel. Making use of the quenching+intercritical reheating-quenching and partitioning (IQ$\&$P) process, a multiphase microstructure which was composed of intercritical ferrite, martensite and well distributed retained austenite (primarily distributed in the prior austenitic grain boundary and the phase boundary) can be obtained in the 0.23C-1.8Mn-1.35Si steel. By means of SEM, XRD and EBSD, microstructures of the steel in different heat treatment stages were characterized. The results indicated that the obtention of the retained austenite was mainly dependent on the following two stages: the first one is the enrichment of the carbon and manganese in the reversed austenite during the intercritical reheating process; the second stage is the secondary enrichment of carbon in retained austenite during the following quenching and partitioning process. After the two stages of element enrichment treatment, more than 10% volume fraction of retained austenite was obtained, and the second stage of treatment plays an important role in the formation and stabilization of the metastable austenite. Due to the strengthening and toughening effect of the widely distrubuted retained austenite, this kind of steel obtained a continuous work hardening ability, and thus achieved a good combination of strength and plasticity. Test results indicated that steel treated by the IQ&P process shows excellent comprehensive mechanical properties: the product of strength and elongation is greater than 26 GPa?%, the yield strength and tensile stength is more than 600 and 900 MPa respectively, the uniform elongationg is above 16\%, and the half thickness size impact toughness at room temperature reaches to 39 J.
[1] McFarlan W H. US Pat, 3378360, 1968
[2] Hayami S, Furukawa T. Microalloying 75. New York: Union Carbide Corp, 1977: 311
[3] Matsumura O, Sakuma Y, Takechi H. Scr Metall, 1987; 21: 1301
[4] Matsumura O, Sakuma Y, Takechi H. ISIJ Int, 1987; 27: 570
[5] Matsumura O, Sakuma Y, Takechi H. ISIJ Int, 1992; 32: 1014
[6] Sugimoto K, Misu M, Kobayashi M, Shirasawa H. ISIJ Int, 1993; 33: 775
[7] Gr¨assel O, Frommeyer G. Mater Sci Technol, 1998; 14: 1213
[8] Bouaziz O, Guelton N. Mater Sci Eng, 2001; A319–321: 246
[9] Barnett M R. Mater Sci Eng, 2007; A464: 1
[10] Speer J G, Matlock D K, De Cooman B C, Schroth J G. Acta Mater, 2003; 51: 2611
[11] Matlock D K, Brautigam V E, Speer J G. Mater Sci Forum, 2003; 426–432: 1089
[12] Sakuma Y, Matsumura O, Takechi H. Metall Mater Trans, 1991; A22: 489
[13] Herrera C, Ponge D, Raabe D. Acta Mater, 2011; 59: 4653
[14] Girault E, Jacques P, Harlet Ph, Mols K, Van Humbeeck J, Aernoudt E, Delannay F. Mater Charact, 1998; 40: 111
[15] Ray A, Dhua S K. Mater Charact, 1996; 37: 1
[16] Speer J G, Streicher A M, Matlock D K, Rizzo F C, Krauss G. In: Damm E B, Merwin M eds., Austenite Formation and Decomposition, Warrendale: TMS, 2003: 505
[17] Edmonds DV, He K, Rizzo F C, De CoomanB C,Matlock D K, Speer J G. Mater Sci Eng, 2006; A438–440: 25
[18] De Cooman B C, Speer J G. In: Lee H C ed., The 3rd Int Conf on Advanced Structural Steels. Gyeongju: The Korean Institute of Metals and Materials, 2006: 798
[19] Streicher A M, Speer J G, Matlock D K, De Cooman B C. In: Speer J G ed., Proc Int Conf on Advanced High Strength Sheet Steels for Automotive Applications. Warrendale: AIST, 2004: 51
[20] Speer J G, Edmonds D V, Rizzo F C, Matlock D K. Opin Curr Solid State Mater Sci, 2004; 8: 219
[21] Sugimoto K, Tsunezawa M, Hojo T, Ikeda S. ISIJ Int, 2004; 44: 1608
[22] Raabe D, Ponge D, Dmitrieva O, Sander B. Scr Mater, 2009; 60: 1141
[23] Shi J, Sun X J, Wang M Q, Hui W J, Dong H, Cao W Q. Scr Mater, 2010; 63: 815
[24] Wang C Y, Shi J, CaoWQ, Dong H. Mater Sci Eng, 2010; A527: 3442
[25] Li H Y, Lu X W, Wu X C, Min Y A, Jin X J. Mater Sci Eng, 2010; A527: 6255
[26] Santofimia M J, Zhao L, Sietsma J. Metall Mater Trans, 2009; A40: 46
[27] Mukherjee M, Mohanty O N, Hashimoto S, Hojo T, Sugimoto K. ISIJ Int, 2006; 46: 316
[28] Fan X. Metallic X–ray Physics. Beijing: Mechanical Industry Press, 1989: 159
(范雄. 金属X射线学. 北京: 机械工业出版社, 1989: 159)
[29] Sugimoto K, Usui N, Kobayashi M, Hashimoto S. ISIJ Int, 1992; 32: 1311
[30] Cullity B D. Elements of X–ray Diffraction. Massachusetts: Addison–Wesley, 1978: 359
[31] Santofimia M J, Nguyen–Minh T, Zhao L, Petrov R, Sabirov I, Sietsma J. Mater Sci Eng, 2010; A527: 6429
[32] Thomas G A, Speer J G, Matlock D K. Metall Mater Trans, 2011; 42A: 3652
[33] Zhang K, Xu W Z, Guo Z H, Rong Y H, Wang M Q, Dong H. Acta Metall Sin, 2011; 47: 489
(张 柯, 许为宗, 郭正洪, 戎咏华, 王毛球, 董 瀚. 金属学报, 2011; 47: 489)
[34] Santofimia M J, Zhao L, Petrov R, Kwakernaak C, Sloof W G, Sietsma J. Acta Mater, 2011; 59: 6059
[35] Nouri A, Saghafian H, Kheirandish Sh. J Iron Steel Res Int, 2010; 17(5): 44
[36] Speich G R, Demarest V A, Miller R L. Metall Mater Trans, 1981; 12A: 1419
[37] Santofimia M J, Zhao L, Sietsma J. Metall Mater Trans, 2011; 42A: 3620
