广义热-扩散-化学-力学耦合作用下的金属高温氧化及破坏机理研究

High temperature oxidation is an important mechanism of the metallic materials ageing and structure failure and chemical reaction has an important influence on the metal or alloys oxidation. The existed chemo-mechanics coupling research is confined to the diffuse-mechanics coupling or too many assumptions are supposed, the related research on the chemical reaction-mechanics-thermo coupling is rarely reported at home and abroad. In this project, comprehensively considering the temperature, diffusion and chemical reaction effects on the mechanical properties of metals, meanwhile considering the Dufour effect and Soret effect, starting from the energy principle, combining with the first and the second law of thermodynamics and using the variational principle and the continuum theory, a generalized coupling thermo-diffusion -chemo-mechanics model is developed, which can completely explain the mechanisms of the metallic oxidation at high temperature. The distributions of the concentration, stress and temperature fields are calculated by using the finite element method, ABAQUS software and the meshless method; The growth of oxidation film is discussed by Level-set or perturbation methods; The destruction mechanism of the oxidation film is revealed by adopting the microcrack initiation and propagation mechanism, and the key factors of high temperature oxidation are given to explore the approaches to preventing and reducing the high temperature oxidation. These results will provide theoretical basis and technical guidance for the heat prevention design and thermal protection of the metal or alloy. This project belongs to multi-disciplinary intersections among solid mechanics, surface physical chemistry, chemical reaction dynamics, elastic theory etc., and there is an important meaning in the academic research.

高温氧化是金属材料老化和结构失效的重要机制，化学反应对此有重要影响。已有的化-力耦合大多局限于扩散-力学耦合或引入过多假设，关于化学反应-力-热耦合的研究国内外鲜有报道。本项目综合考虑温度、扩散、化学反应对金属力学性能的影响，同时考虑Dufour和Soret效应，从能量原理出发，结合热力学第一、二定律，运用变分原理和连续介质理论，建立全面反映金属高温氧化的广义热-扩散-化学-力学耦合模型理论。采用有限元方法、商业软件ABAQUS及无网格方法计算浓度场、应力场及温度场分布并与实验结果对比；通过水平集方法、摄动法探讨氧化膜生长规律；运用微裂纹萌生与扩展机理揭示氧化膜诱发破坏规律，给出抗高温氧化的关键因素，寻求抑制或减小高温氧化损失的途径，为金属及合金防热设计及热防护提供理论依据和技术指导。本项目研究属于固体力学、表面物理化学、化学反应动力学、弹性理论等多学科的交叉，在学术研究方面具有重要意义。

高温氧化是金属材料老化和结构失效的重要机制，化学反应对此有重要影响。已有的化力耦合大多局限于扩散-力学耦合或引入过多假设，关于化学反应-力-热耦合的研究国内外鲜有报道。本项目综合考虑温度、扩散、化学反应、应变梯度对金属力学性能的影响，同时考虑Du four和Soret效应，从能量原理出发，结合热力学第一、二定律，运用变分原理和连续介质理论，建立全面反映金属高温氧化的广义热-扩散-化学-力学耦合模型理论。依据建立的变分原理，分别给出了考虑固有应变、蠕变效应的金属高温氧化的残余应力分析模型；考虑外部载荷、生长应变、蠕变和弯曲变形的金属高温氧化的残余应力分析模型；单轴应力状态和单轴应变状态下一维扩散-化学-力学耦合分析。然后运用有限元或分离变量的方法对其进行了数值计算，计算结果表明：生长常数、蠕变系数、外部载荷、金属基体厚度对氧化层和金属基体应力演化有很大影响且扩散、化学反应和应力在氧化过程中存在着较强的交互作用。本项目研究属于固体力学、表面物理化学、化学反应动力学、弹性理论等多学科的交叉，在学术研究方面具有重要意义。