Characterization of phase structure and grain orientation of martensite-austenite island in duplex steel by transmission-electron backscatter diffraction
JIN Chuan-wei, ZHANG Ke, WU Yuan-yuan
Institute of Research of Iron and Steel, Jiangsu Province and Sha Steel, Zhangjiagang 215625, China
Abstract：In order to investigate the relationship between fine structure and grain misorientation of martensite-austenite island (M-A island) in high-strength low-yield ratio dual-phase steel, the self-made transmission-electron backscatter diffraction (T-EBSD) sample stage and transmission electron microscope samples were used for the nanoscale high-resolution electron back scattering diffraction (EBSD) characterization on scanning electron microscope (SEM). By optimizing the parameters including working voltage, tilting angle, working distance, probe distance and step size, the optimal experimental conditions were determined as follows: the working voltage was 30kV, the tilting angle was 30°~38° and the step size was 15nm. Finally, the high quality transmission Kikuchi pattern was obtained, which achieved a fine characterization of microstructure to increase the resolution of conventional EBSD by one order of magnitude. Meanwhile, it was verified by high resolution microscopy of transmission electron microscope (HRTEM). The results of EBSD analysis showed that there were four structures in M-A island of LYR690 steel, including ultrafine ferrite, ferrite and austenite mixed phase, retained austenite and martensite. The retained austenite mainly existed in two forms: one was an individual crystal grain at level of several hundred nanometers, which had a high angle misorientation of more than 15° with the surrounding ferrite, and another was the fine austenitic structure distributed in ferrite grains, which had a misorientation of less than 10° with ferrite grains.
金传伟, 张珂, 吴园园. 透射-电子背散射衍射技术表征双相钢中马氏体-奥氏体岛的相结构及晶粒取向[J]. 冶金分析, 2019, 39(12): 1-7.
JIN Chuan-wei, ZHANG Ke, WU Yuan-yuan. Characterization of phase structure and grain orientation of martensite-austenite island in duplex steel by transmission-electron backscatter diffraction. , 2019, 39(12): 1-7.
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