Environmentally Assisted Cracking of High Strength Al Alloys - Transition from Initiation to Sustainable Cracking

高强度铝合金的环境辅助裂解 - 从起始裂解到可持续裂解的转变

• 批准号: 2879407
• 金额: --
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2879407
• 关键词: Environmentally; Assisted; Cracking; Strength; Al

Advanced high strength Al-Zn-Mg-Cu alloys are widely employed in the aerospace industry, owing to their competitive cost and high strength-to-density ratio. In modern aircraft design these materials are frequently deployed in large integral components manufactured from thick-gauge hot-rolled plates. However, it has been discovered that they can be susceptible to 'Environmentally Assisted Cracking' (EAC) in warm humid air environments. This is a complex hybrid chemical-mechanical damage mechanism whereby a combination of a high stress, water, and chemical reaction, with active phases within the material, generates hydrogen which enters the material and causes grain boundary embrittlement. However, several different fracture processes have been observed, as a function of the material, load, and environmental conditions.The aim of this project is to exploit recent advances in 3D characterization techniques to improve our current poor understanding of how the local sub-surface microstructure and the environment within an embryo crack controls the transition from initiation to sustainable self-propagating cracks with different mechanistic regimes. This will include using in-situ and multi-scale 3D imaging techniques, by combing very high resolution tomography and destructive serial sectioning electron microscopy, to probe both the local environment formed within an embryonic crack and the interaction with the local microstructure and chemistry. In particular, by decoupling the effects of grain structure and precipitate type/chemistry, and the exposure conditions, the project will aim to determine why some cracks go on to become self-sustaining and others die, and why there are several regimes where different crack propagation mechanisms dominate.

先进的高强度Al-Zn-Mg-Cu合金因其具有竞争力的成本和高强度密度比而广泛应用于航空航天工业。在现代飞机设计中，这些材料经常应用于由厚规格热轧板制造的大型整体部件中。然而，人们发现它们在温暖潮湿的空气环境中很容易受到“环境辅助破裂”（EAC）的影响。这是一种复杂的混合化学机械损伤机制，其中高应力、水和化学反应与材料内的活性相相结合，产生氢进入材料并导致晶界脆化。然而，已经观察到了几种不同的断裂过程，作为材料、载荷和环境条件的函数。该项目的目的是利用 3D 表征技术的最新进展，以改善我们目前对局部地下如何形成的了解。胚胎裂纹内的微观结构和环境控制着不同机制机制从萌生裂纹到可持续自蔓延裂纹的转变。这将包括使用原位和多尺度 3D 成像技术，通过结合超高分辨率断层扫描和破坏性连续切片电子显微镜，来探测胚胎裂纹内形成的局部环境以及与局部微观结构和化学成分的相互作用。特别是，通过解耦晶粒结构和沉淀物类型/化学以及暴露条件的影响，该项目的目标是确定为什么一些裂纹会继续自我维持而另一些裂纹会消失，以及为什么存在不同裂纹的几种状态。传播机制占主导地位。