高温结构材料以其良好的高温服役性能，成为航空航天、燃气轮机、核反应堆等战略性技术的支撑。发展面向高温结构材料的在线测量方法，研究材料的高温力学行为，揭示其力-化学耦合机理，对高温结构材料的性能提升具有重要意义。然而，高温环境的动态性、强干扰性，材料微观行为演化的复杂性、强耦合性，对在线测量和力-化学耦合机理的研究造成了巨大挑战。因此，本文针对高温结构材料在线测量方法及其力-化学耦合行为，开展了如下研究工作：首先，针对高温光学测量中辐射光和反射光相互干扰的难题，发展了基于光学信号分离的高精度温度变形同步在线测量方法。通过光学平衡关系提出了一种迭代算法，同时引入收敛因子，分别提取辐射光和反射光强度，实现了更宽温域下温度场、变形场的同步在线测量，测量精度较现有方法得到显著提升。开展了碳/碳化硅（C/SiC）复合材料试件的氧丙烷火焰烧蚀实验，验证了该方法的有效性。其次，针对高温光学成像中多通道信号间串扰的问题，发展了一种基于实验标定的信号串扰校正方法。通过标定分别获取了补偿强度恒定条件下曝光时间与图像灰度的响应关系曲线，以及相机通道间的串扰特性，实现了高动态环境下通道间串扰对温度和变形测量影响的分析，提高了温度变形同步测量的精度和适用范围。然后，针对高温结构材料微纳尺度下力-化学耦合行为的在线测量难题，提出了一种基于表面标记物与数字图像处理的在线测量方法，通过制备压痕、微柱作为图像识别特征点，利用数字图像处理实现了全场变形的测量，同时通过高温扫描探针显微成像技术实现了表面非均匀氧化形貌的测量。通过对应变分布与氧化生长速率的耦合分析，阐明了应力与氧化生长之间的关系。最后，针对当前力-化学耦合机理不明晰、模型不完善等问题，基于对高温氧化过程与氧化膜中生长应力的分析，提出了考虑粒子双向扩散行为及界面反应过程的应力-氧化耦合理论模型。针对阳离子外向扩散和阴离子内向扩散主导的氧化过程，发展了双向扩散下的力-化学耦合模型。在此基础上，将氧化进一步分解为气体/氧化膜界面吸附、粒子跨膜输运、氧化膜/基底界面反应三个过程，构建了描述氧化生长动力学的耦合方程，揭示了应力与氧化的不同阶段之间的耦合作用机制。
Due to the excellent high temperature service performance, high temperature structural materials have become the key support for strategic technologies such as aerospace, gas turbines and nuclear reactors, etc. Developing the in-situ measurement methods, studying the mechanical behavior under high temperature, and on this basis revealing the chemo-mechanical coupling mechanism, is of great significance for performance improvement of high temperature structural materials. However, the dynamic and strong interference of high temperature environment, as well as the complexity and strong coupling effect of microscopic behavior evolution of materials, brings great challenges to the study of in-situ measurement methods and chemo-mechanical coupling mechanism. Therefore, focusing on the in-situ measurement methods of high-temperature structural materials and its chemo-mechanical coupling effect, this paper carries out the following research work:Firstly, aiming at the mutual interference between radiation and reflected in high temperature optical measurement, a high accuracy, synchronous and in-situ measurement method of temperature and deformation based on optical signal separation is developed. Through the optical equilibrium relationship and the introduction of convergence factor, an iterative algorithm is proposed. The intensity of radiation and reflected light are separated separately, which realized the measurement of full-field temperature and deformation in a wide temperature domain. The measurement accuracy is significantly improved compared with the original methods. Oxy-propane flame ablation experiment of C/SiC composite is carried out, which verify the effectiveness of this method.Secondly, aiming at the crosstalk effect of multi-channel signals in high temperature optical imaging, a crosstalk correction method based on experimental calibration is developed. The relationship between exposure time and image gray level under constant compensation intensity, as well as the crosstalk characteristics between camera channels is obtained by calibration. The effect of channel crosstalk on temperature and deformation measurement in dynamic environment is analyzed, and the accuracy and application range of the synchronous measurement method are improved. Then, aiming at the in-situ measurement difficulties of chemo-mechanical coupling behavior of high-temperature structural materials at micro/nano scale, an in-situ measurement method based on surface markers and digital image processing is developed. The indentation and microcolumn are selected as the feature points for image recognition, and the full-field deformation is measured based on digital image processing. Meanwhile, the non-uniform oxidation morphology of the surface is measured by high temperature scanning probe microscopic (HT SPM) technology. The relationship between stress and oxidation growth is illustrated by comprehensive analysis of strain distribution and oxidation growth rate.Finally, in view of the chemo-mechanical coupling mechanism is unclear and the model is incomplete currently, we propose stress-oxidation coupling theoretical models based on the analysis of the high temperature oxidation process and growth stress mechanism, which take into account the bidirectional diffusion behavior of particles and the interfacial reaction process. Aiming at the oxidation process dominated by outward diffusion of cation and inward diffusion of anion, a chemo-mechanical coupling model is developed. On this basis, the oxidation is further decomposed into three processes, i.e, adsorption of particles at gas/oxide film interface, transport across the film, and reaction at oxide film/substrate interface. The coupling equation describing the oxidation growth kinetics is constructed and the coupling mechanisms between stress and oxidation at different stages are revealed.
