Kinetics of non-equilibrium grain-boundary segregation

摘要: I. During the isothermal holding at a constant temperature after sample is cooled quickly enough from higher critical time exists, which maximum level of NGS will occur. This most characteristic aspect isotherm. The formula was given in Section 2 to predict occur during 2. A kinetic model suggested 3 5 this paper, along same thought structure as McLean's EGS. thermodynamic equation for first established describing concentration that can due cooling between any two temperatures, and then an by solving Fick's diffusion based on equation. Based grain boundary segregation calculated using effective method correction factor method. 3. cooling. different rates produce levels NGS. There certain rate kind material, when material appear. called another 4. In 6, we such new describe interactions kinds solute atom with vacancy NGS: binary solution solvent 3, if has binding energy beyond suitable range occur, little or no would binary. If 1 attraction pairs 1-2 stronger than 1-3 2-3 (α' > 0), also ternary alloy added alloy. NGCS. 5. effects applied stress segregation/dilution been set equations have 7. simulation good accordance observations sulfur phosphorus grain-boundary steels. It following assumptions: (1) boundaries work free sources vacancies compressive exerted them sinks tension exerted. (2) Oversaturated induced be combined atoms form complexes. (3) flux complexes concomitant but reverse center. (4) stress, NGS/NGD, are controlled all balance these fluxes. As result balance, they aspect, time, manner similar quenching. 6. For some elements, quenched quenching medium rate, resultant sum EGS produced Such vary constant.