Knowledge based design of crack and erosion damage healing nanolaminates

今天，组件的性能设计使得它们在必须进行“外部”修理或更换新组件之前，在给定时间内满足各种环境中的操作需求。自修复材料允许基于损伤管理的设计概念，其中在操作期间造成的损伤可以自主修复。结果表明，Mn+1AXN相Ti_3AlC_2、Ti_2AlC和Cr_2AlC具有自修复行为。在高温下，裂纹被MAX相中M和A元素的氧化产物填充并愈合。裂纹愈合后，断裂强度恢复到原始材料的水平。MAX相是表现出陶瓷和金属性质的纳米层压材料。由于其抗氧化和耐腐蚀性，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，已经表明MAX相Cr2 AlC表现出优异的耐腐蚀性。到目前为止，自修复材料的基本物理和化学材料设计原则尚未确定。因此，本计画旨在辨识与了解这些原理，以实现裂缝与冲蚀损伤愈合材料的知识化设计。基于对Cr_（2-x）M_xAl_（1-y）AyC（M = Ti，Hf，Zr; A = Si，B）稳定性的从头计算，确定并合成了适合实验的相。裂纹愈合动力学将作为一个函数的元素M和A的浓度的实验和通过建模的方式进行研究。原则上，腐蚀损伤的自愈似乎是可能的，但还需要实验证明。该项目的长期愿景是预测MAX阶段的裂缝和侵蚀损伤管理能力，作为成分，温度，时间和环境的函数。

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.