Knowledge based design of crack and erosion damage healing nanolaminates

今天，组件的属性被设计为在必须“外部”修复或更换新组件之前，满足给定时间内各种环境中的操作需求。自我修复材料允许基于损伤管理的设计理念，其中在操作过程中造成的损伤可以自动修复。结果表明，MN+1AXN相Ti3AlC2、Ti2AlC和Cr2AlC具有自主自愈行为。裂纹由MAX相中M和A元素在高温下的氧化产物填充并因此愈合。裂纹愈合后，断裂强度恢复到原始材料的水平。MAX相是同时具有陶瓷和金属特性的纳米层状物。由于其抗氧化性和耐腐蚀性，它可以在高温和腐蚀性环境中使用。与传统的高温材料不同，MAX相金属陶瓷易于加工。此外，还表明最大相Cr2AlC具有良好的抗冲蚀性能。到目前为止，自愈合材料的基本物理和化学材料设计原则还没有确定。因此，本项目旨在识别和理解这些原则，以实现基于知识的裂纹和冲蚀损伤修复材料的设计。在对Cr2-xMxAl1-yAyC(M=Ti，Hf，Zr；A=Si，B)稳定性从头算的基础上，确定并合成了适合实验的相。裂纹愈合动力学将作为元素M和A的浓度的函数通过实验和模拟来研究。原则上，侵蚀损伤的自我修复似乎是可能的，但还需要实验证明。该项目的长期愿景是预测作为成分、温度、时间和环境的函数的最大阶段的裂纹和侵蚀损伤管理的能力。

Today, the properties of components are designed such that they meet operational demands in various environments for a given time before they have to be repaired “externally” or replaced by new ones. Self-healing materials allow for a design concept based on damage management where damage that is inflicted during operation can be healed autonomously. It has been shown that the MN+1AXN phases Ti3AlC2, Ti2AlC and Cr2AlC exhibit autonomous self-healing behaviour. Cracks are filled and hence healed by oxidation products of the M and A elements in the MAX phase at high operating temperatures. After crack healing the fracture strength is recovered to the level of the virgin material. MAX phases are nanolaminates exhibiting both ceramic and metallic properties. Due to its oxidation and corrosion resistance, it can be used at high temperatures and in aggressive environments. Unlike conventional high temperature materials, MAX phase metallo-ceramics are easily machinable. Furthermore, it has been shown that the MAX phase Cr2AlC exhibits excellent erosion resistance. So far, basic physical and chemical materials design principles for self-healing materials have not been identified. Therefore, this project aims at identifying and understanding these principles to realize knowledge-based design of crack and erosion damage healing materials. Based on ab initio calculations of the stability of Cr2-xMxAl1-yAyC (M = Ti, Hf, Zr; A = Si, B), phases suitable for experiments are determined and synthesized. The crack healing kinetics will be investigated as a function of the concentrations of the elements M and A both experimentally and by means of modelling. In principal, self-healing of erosion damage appears possible, but yet has to be demonstrated experimentally. The long-term vision of this project is to predict the capability of a MAX phases for crack and erosion damage management as a function of composition, temperature, time and environment.