An Electron Microscopy Study of Vein-like Grain Boundary Microstructure in Nitrocarburized Low Carbon Steels
来源期刊：JOURNAL OF MATERIALS SCIENCE TECHNOLOG2013年第7期
论文作者：Wanglin Chen Cuilan Wu Jianghua Chen Aigui He
文章页码：669 - 672
摘 要：<正>The coarsened grain boundaries（GBs） with vein-like morphology frequently appear in the nitrogen diffusion layer of nitrocarburized carbon steels.The electron probe X-ray microanalysis shows that such vein-like GBs are rich in nitrogen and carbon atoms.Transmission electron microscopy and scanning electron microscopy further reveal that the coarsened GBs consist ofγ’-nitrocarbide（Fe4（C,N）） andε-nitrocarbide lamellas that are formed during nitrocarburizing due to high nitrogen concentration at GBs.It is shown that many of {111}<112> micro twins exist in the y’-phase lamellas and thin e-phase slices prefer to nucleate at their twin boundaries with the orientation relationship of {0001}ε//{111}γ’.Upon growing large y’-lamellas may become faceted and thin e-lamellas may grow thicker and become the main portions in the vein-like GBs.The microstructure evolution occurring in the vein-like GBs can be depicted as:α+[N]/[C]→>γ’ +[C,N]→ε-nitrocarbides.
Wanglin Chen，Cuilan Wu，Jianghua Chen，Aigui He
Center of High Resolution Electron Microscopy,College of Materials Science and Engineering,Hunan University
摘 要：<正>The coarsened grain boundaries（GBs） with vein-like morphology frequently appear in the nitrogen diffusion layer of nitrocarburized carbon steels.The electron probe X-ray microanalysis shows that such vein-like GBs are rich in nitrogen and carbon atoms.Transmission electron microscopy and scanning electron microscopy further reveal that the coarsened GBs consist ofγ’-nitrocarbide（Fe4（C,N）） andε-nitrocarbide lamellas that are formed during nitrocarburizing due to high nitrogen concentration at GBs.It is shown that many of {111}<112> micro twins exist in the y’-phase lamellas and thin e-phase slices prefer to nucleate at their twin boundaries with the orientation relationship of {0001}ε//{111}γ’.Upon growing large y’-lamellas may become faceted and thin e-lamellas may grow thicker and become the main portions in the vein-like GBs.The microstructure evolution occurring in the vein-like GBs can be depicted as:α+[N]/[C]→>γ’ +[C,N]→ε-nitrocarbides.
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