Microstructure,crystallography and nucleation mechanism of NANOBAIN steel
来源期刊：International Journal of Minerals Metallurgy and Materials2013年第12期
论文作者：Yao Huang Ai-min Zhao Jian-guo He Xiao-pei Wang Zhi-gang Wang Liang Qi
文章页码：1155 - 1163
摘 要：The microstructure of bainite ferrite in NANOBAIN steel transformed at different temperatures was investigated by scanning electron microscopy,transmission electron microscopy,electron back-scattered di?raction,and vickers hardness tester in detail.It is found that the average width of bainitic ferrite（BF）plates can be refined to be thinner with the reduction of temperature（473-573 K）,and the bainitic ferrite plates can reach up to 20-74 nm at 473 K.Crystallographic analysis reveals that the bainitic ferrite laths are close to the Nishiyama-Wasserman orientation relationship with their parent austenite.Temperature shows a significant effect on the variant selection,and a decrease in temperature generally weakens the variant selection.Thermodynamic analyses indicates that the Lacher,Fowler and Guggenheim（LFG）model is more suitable than the Kaufman,Radcli?e and Cohen（KRC）model dealing with NANOBAIN steel at a low temperature range.The free energy change ?G γ→ BF is about –1500 J·mol-1 at 473 K,which indicates that nucleation in NANOBAIN steel is the shear mechanism.Finally,the formation of carbon poor regions is thermodynamically possible,and the existence of carbon poor regions can greatly increase the possibility of the shear mechanism.
Yao Huang1，Ai-min Zhao1，Jian-guo He1，Xiao-pei Wang1，Zhi-gang Wang1,2，Liang Qi1,2
1. Metallurgy Engineering Research Institute,University of Science and Technology Beijing2. School of Material Science and Engineering,Jiangxi University of Science and Technology
摘 要：The microstructure of bainite ferrite in NANOBAIN steel transformed at different temperatures was investigated by scanning electron microscopy,transmission electron microscopy,electron back-scattered di?raction,and vickers hardness tester in detail.It is found that the average width of bainitic ferrite（BF）plates can be refined to be thinner with the reduction of temperature（473-573 K）,and the bainitic ferrite plates can reach up to 20-74 nm at 473 K.Crystallographic analysis reveals that the bainitic ferrite laths are close to the Nishiyama-Wasserman orientation relationship with their parent austenite.Temperature shows a significant effect on the variant selection,and a decrease in temperature generally weakens the variant selection.Thermodynamic analyses indicates that the Lacher,Fowler and Guggenheim（LFG）model is more suitable than the Kaufman,Radcli?e and Cohen（KRC）model dealing with NANOBAIN steel at a low temperature range.The free energy change ?G γ→ BF is about –1500 J·mol-1 at 473 K,which indicates that nucleation in NANOBAIN steel is the shear mechanism.Finally,the formation of carbon poor regions is thermodynamically possible,and the existence of carbon poor regions can greatly increase the possibility of the shear mechanism.
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