Stress-induced non-equilibrium grain boundary segregation of phosphorus in a Cr–Mo low alloy steel |
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Authors: | S-H Song J Wu D-Y Wang L-Q Weng L Zheng |
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Affiliation: | aDepartment of Materials Science and Engineering, Shenzhen Graduate School, Harbin Institute of Technology, Xili, Shenzhen 518055, China bCentral Iron and Steel Research Institute, Superalloy Department, No. 76 Xuyuan Nanlu, Beijing 100081, China |
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Abstract: | Grain boundary segregation of phosphorus under a 40 MPa tensile stress at 520 °C in a 0.025 wt.% P-doped 2.25Cr1Mo steel, which has already been thermally equilibrated, is examined using Auger electron spectroscopy. The segregation of phosphorus during stress-ageing has a non-equilibrium characteristic, i.e. it is non-equilibrium segregation. The segregation level first increases with increasing stress-ageing time until about 0.5 h and then diminishes with further increasing stress-ageing time, leading the boundary concentration of phosphorus to return to its thermal equilibrium value after ageing for about 15 h. Therefore, the critical time for this non-equilibrium grain boundary segregation of phosphorus is about 0.5 h at which the segregation is peaked. At this critical time, the boundary concentration of phosphorus is about 20.5 at.%, which is about 4.5 at.% higher than its thermal equilibrium level. Xu's kinetic model for stress-induced grain boundary segregation T.D. Xu, Philos. Mag. 83 (2003) 889–899; T.D. Xu, B.-Y. Cheng, Prog. Mater. Sci. 49 (2) (2004) 109–208] is used to analyse the experimental results, demonstrating that the measured data may be well simulated by the model. |
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Keywords: | Non-equilibrium segregation Grain boundary Ferritic steels Pressure vessels |
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