Microstructure Evolution of Undercooled Austenite during Deformation for Medium-Carbon Si-Mn Steel

Abstract:

The microstructure evolution of a medium-carbon Si-Mn steel during deformation of undercooled austenite at different degree of deformation, temperatures and strain rates has been investigated by means of a hot compression simulation test, metallographic microscope, scanning electron microscope and transmission electron microscopy. Also, the mechanism of carbide spheroidized during deformed process has been discussed. The experiment results demonstrate that the process of evolution experienced three stages: that is, strain-induced transformation, austenite eutectoid decomposed to carbides and ferrite matrix, and spheroidization of pearlite at the range of A₃-Ar₃. The austenitic grains would be refined for the extra-product of ferrite above the Ar₃. The eutectoid reaction was induced on the grain boundaries of ferrite and non-transformed austenite and deformation bands with the increasing volume of deformation. An optimum combination of deformation temperature and strain rate is important to obtian the dulplex microstructure consisting of ultrafine ferrites and dispersed carbide particles. The fine spheroidized microstructures are obtained while the deformed temperature reaches 650°C with ≥1.0, meanwhile, The carbides precipate in globular and shot-rod shapes. Keywords: Medium-carbon Si-Mn steel, Undercooled austentite, Microstructure evolution, Deformation induced transformation, Carbide spheroidization

• Periodical: Materials Science Forum (Volumes 704-705)
• Pages: 903-906
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.704-705.903
• Online since: December 2011
• Authors: Yun Li Feng, Shao Qiang Yuan, Meng Song
• Keywords: Carbide Spheroidization, Deformation Induced Transformation, Medium-Carbon Si-Mn Steel, Micro-Structure Evolution, Undercooled Austentite

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