溶质界面偏聚的富集比波动性量化及动力学方程准确度修正

Segregation of solute atoms at surface, grain boundary or phase boundary is an important phenomenon which affects the mechanical, physical and chemical properties of materials significantly. McLean's equation, founded by introducing enrichment ratio and considering it as a constant, is widely used to characterize kinetics of grain boundary segregation, analogized to surface segregation, and extended to phase boundary segregation. However, the intrinsic and strong volatility of enrichment ration leads to very low accuracy of the calculation by McLean's equation. Therefore, on the bases of identical essences of these three kinds of segregation and preliminary results of the applicant, the experimental study on segregation kinetics, specialty of lattice substitution, and process of jumping layer by layer will be carried out in the present project, in order to explore the volatility of enrichment ration and approve the rationality of special concentration and concentration difference ratio. At the same time, the model of diffusion mechanism of solute segregation and the formula of the volatility of enrichment ration will be approved and promoted on the basis of experimental results, thermodynamic theory and crystallographic knowledge. Besides, the nature of special concentration will be discovered and its formula will be given to set up the modified kinetics proposed by the applicant. Based on the experimental results, theoretical model and the derived equations, computer simulation will be initiated subsequently to obtain exacter values of segregation energy, concentration error ratio, et al. The present project will achieve the promotion of calculated accuracy of kinetic equation, and provide theoretical basis and instructing scheme to the forecast and control of the interface compositions and the materials' properties.

溶质在表面、晶界、相界处的偏聚是影响材料力学、物理、化学性能的重要因素。引入富集比参量并规定为定值而建立的McLean动力学方程，被广泛用于晶界偏聚和借用于表面偏聚，并可推广于相界偏聚，但富集比本质上的强烈波动性导致方程计算准确度很低。由此，本项目基于三种偏聚产生原因的相同性和申请人的初步成果，开展偏聚动力学、晶格占位、原子跃迁等实验研究，掌握富集比的波动性，验证特定浓度、浓度误差比等参量；然后基于实验结果、热力学理论和晶体学知识，验证和完善申请人初步建立的“溶质界面偏聚扩散机制”模型及富集比波动性量化公式，重点揭示特定浓度的产生原因并进行量化表征，以此获得高准确度偏聚动力学修正方程；同时依据实验结果、理论模型及相关公式，模拟计算出偏聚自由能、特定浓度、浓度误差比等重要参量的更准确结果。本项目可望提升偏聚动力学方程的准确度，为界面成分及材料性能的预报与控制提供更可靠的理论依据和指导方案。

溶质在表面、晶界和相界处的偏聚是影响材料力学、物理以及化学性能的重要因素。引入富集比参量并规定为定值而建立的McLean动力学方程，目前被广泛用于晶界偏聚并借用于表面偏聚，而且可以推广于相界偏聚。富集比本质上的强烈波动性导致方程计算准确度很低，本项目基于三种偏聚产生原因的相同性和申请人的初步成果，开展了偏聚动力学、晶格占位以及原子跃迁等的实验研究，掌握了富集比的波动性，验证了特定浓度、浓度误差比等参量，并基于实验结果、热力学理论和晶体学知识，验证和完善了“溶质界面偏聚扩散机制”模型和富集比波动性的量化公式，揭示了特定浓度产生的原因并进行了量化表征，获得了高准确度偏聚动力学修正方程，依据实验结果、理论模型及相关公式模拟计算出了偏聚自由能、特定浓度、浓度误差比等重要参量的更准确结果。同时，引入了挥发条件，建立了挥发条件下表面偏聚模型。本项目可望提升偏聚动力学方程的准确度，为界面成分及材料性能的预报与控制提供更切实可靠的理论依据和指导方案。