Mechanism of residual austenite in medium-carbon bainite steel of 30 GPa·% level
YAN Heng1,2, HU Feng1,2,3, WANG Kun1,2, ZHOU Song-bo1,2, ZHOU Wen1,2, WU Kai-ming1,2,3,4
1. Hubei Collaborative Innovation Center for Advanced Steels, Wuhan University of Science and Technology, Wuhan 430081, Hubei, China; 2. International Research Institute for Steel Technology, Wuhan University of Science and Technology, Wuhan 430081, Hubei, China; 3. Hubei Province Key Laboratory of Systems Science in Metallurgical Process, Wuhan University of Science and Technology, Wuhan 430081, Hubei, China; 4. Metals Valley and Band (Foshan) Metallic Composite Co., Ltd., Foshan 528000, Guangdong, China
Abstract:The purpose of this experiment was to study the influence of the shape and distribution of residual austenite on the product of strength and ductility of medium-carbon bainite steel to further enhance the strength and ductility of the medium-carbon bainite. Testing techniques such as scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to test different samples for comparison of the microstructure. XRD was used to detect the content of the samples. Tensile test was used to test mechanical properties of the samples. The results showed that the partial replacement of Si by Al could accelerate the bainite transformation process,which could also effectively refine the bainite lath and the residual austenite size. Besides,the partial replacement of Si by Al increased the carbon content in the residual austenite which promoted the formation of film residual austenite. Thus,necking of the samples was delayed. Finally,the elongation of the samples was greatly improved. The strength-ductility of 0.26Si-1.1Al samples under the process of isothermal annealing at 300 ℃ for 8 h was raised to the level of 30 GPa·%.
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