| The segregation of alloy elements, especially the trace elements at grain boundaries, has an important influence on the mechanical behavior of engineering materials. It has been an interesting thing to metallurgists and metarial engineers. The segregation of solute atoms at grain boundaries may be classified into equilibrium segregation and non-equilibrium segregation. The study on equilibrium grain boundaries segregation has started long before, and its theory has approached almost perfect. However, there are so much unknown about the non-equilibrium grain boundary segregation, especially the stress-induced non-equilibrium grain boundary segregation.In the present work, a 2.25Cr-1Mo steel was selected as the experimental material. Xu's model was used to explain the non-equilibrium grain boundary segregation of phosphorus induced by a low tensile stress. And seven kinds of phosphorus concentrations were measured by Auger electron spectroscopy (AES), which were aged at 520℃, 40 MPa for different times.When the materials were aged at 520℃with a low tensile stress 40 MPa, non-equilibrium grain boundaries segregation would occur. The critical time was 30 min. After that, the grain boundary segregation level decreased slowly until reaching equilibrium boundary concentration after ageing for about 15 h.Misra RDK's explanation to the stress-induced non-equilibrium grain-boundary segregation was based on the diffusional creep theory. However when there were no creep and other deformation, Xu model is more applicable. That was verified by the experimental results.Based on the simulations with the use of Xu model, tensile stress can increase the diffusion coefficient of vacancy-phosphorus complexes and reduce that of phosphorus atoms. The relationship between phosphorus diffusion coefficients and stress aging time during the de-segration process may be expressed as Di (m2 s-1) =10(-0.00121×t - 20.73485) (t is in min).
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