Korean Journal of Materials Research, Vol.30, No.2, 87-92, February, 2020
오스템퍼링 시간에 따른 초고강도 나노 베이나이트강의 미세조직과 기계적 특성
Effect of Austempering Time on the Microstructure and Mechanical Properties of Ultra-High Strength Nanostructured Bainitic Steels
This study deals with the effects of austempering time on the microstructure and mechanical properties of ultrahigh strength nanostructured bainitic steels with high carbon and silicon contents. The steels are composed of bainite, martensite and retained austenite by austempering and quenching. As the duration of austempering increases, the thickness of bainitic ferrite increases, but the thickness of retained austenite decreases. Some retained austenites with lower stability are more easily transformed to martensite during tensile testing, which has a detrimental effect on the elongation due to the brittleness of transformed martensite. With increasing austempering time, the hardness decreased and then remained stable because the transformation to nanostructured bainite compensates for the decrease in the volume fraction of martensite. Charpy impact test results indicated that increasing austempering time improved the impact toughness because the formation of brittle martensite was prevented by the decreased fraction and increased stability of retained austenite.
Keywords:nanostructured bainite;austempering;retained austenite;mechanical property;ultra-high strength
- bhadeshia HKD, Edmonds DV, Met. Sci., 17, 411 (1983)
- Caballero FG, Miller MK, Babu SS, Garcia-Mateo C, Acta Mater., 55, 381 (2007)
- Kozeschnik E, Bhadeshia HKDH, Mater. Sci. Technol., 24, 343 (2008)
- Zhilyaev AP, Langdon TG, Prog. Mater. Sci., 53(6), 893 (2008)
- Valiev RZ, Langdon TG, Prog. Mater. Sci., 51(7), 881 (2006)
- Bhadeshia HKDH, Mater. Sci. Technol., 21, 1293 (2005)
- Donges B, Giertler A, Krupp U, Fritzen CP, Christ HJ, Mater. Sci. Eng. A, 589, 146 (2014)
- Das S, Kundu S, Haldar A, Mater. Sci. Forum, 702, 939 (2012)
- Lee DJ, Kim MS, Ku GE, Heo SH, Kim NY, Lee JM, Korean J. Met. Mater., 56, 221 (2018)
- Garcia-Mateo C, Caballero FG, Bhadeshia HKDH, ISIJ Int., 43, 1238 (2003)
- Hillert M, Hoglund L, Agren J, Metall. Mater. Trans. A-Phys. Metall. Mater. Sci., 35, 3693 (2004)
- Sung HK, Shin SY, Hwang B, Lee CG, Kim NJ, Lee S, Korean J. Met. Mater., 48, 798 (2010)
- Lee JM, Lee SI, Lim HS, Hwang B, Korean J. Mater. Res., 28, 522 (2018)
- Miihkinen VTT, Edmonds DV, Mater. Sci. Technol., 3, 422 (1987)
- Garcia-Mateo C, Caballero FG, Bhadeshia HKDH, ISIJ Int., 43, 1821 (2003)
- Zhang M, Wang TS, Wang YH, Yang J, Zhang FC, Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process., 568, 123 (2013)
- Garcia-Mateo C, Caballero FG, Mater. Trans., 46, 1839 (2005)
- Caballero FG, Garcia-Mateo C, Santofimia MJ, Miller MK, Garcia de Andresa C, Acta Mater., 57, 8 (2009)
- Porter DA, Easterling KE, Sherif M, Phase Transformations in Metals and Alloys, 3th ed., p.536, CRC press, Florida, USA (2009).
- Krauss G, Principles of Heat Treatment of Steel, p.291, Metals Park : American Society for Metals, Ohio, USA (1980).
- Dieter GE, Mechanical Metallurgy, p.751, McGraw-Hill, New York, USA (1986).
- Gao G, Zhang H, Gui X, Luo P, Tan Z, Bai B, Acta Mater., 76, 425 (2014)
- Zhou Q, Qian LH, Tan J, Meng JY, Zhang FC, Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process., 578, 370 (2013)
- Tomita Y, Okawa T, Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process., 172, 145 (1993)
- Bhadeshia HKDH, Proc. Math. Phys. Eng. Sci., 466, 3 (2009)
- Hertzberg RW, Deformation and Fracture Mechanics of Engineering Materials, 4th ed., p.786, John Wiley & Sons, New Jersey, USA (1996).