Discovering atomic scale mechanisms of stress corrosion cracking in aerospace titanium alloys

发现航空航天钛合金应力腐蚀开裂的原子尺度机制

• 批准号: 2573461
• 金额: --
• 依托单位: King's College London
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2573461
• 关键词: Discovering; atomic; scale; mechanisms; stress

Accurate computational construction of screw and edge dislocations, in a titanium/titanium dioxide system, will be achieved by utilising the multi-scale atomistic approach of "embedding": a technique whereby a self-consistent polarisable-ion tight binding model governs the energies of atoms in the non-linear stressed 'cores' of dislocations, while a bond order potential model- which provides a faster, but less accurate, approach to modelling atomic energies-governs the regions of atoms outside of the core. The effects of interstitial oxygen on the dynamics of dislocations, and interactions between dislocation systems of various types, between and within the two different mediums, will be studied. Enhanced stress fields, generated from dislocation pile up at the interface between Titanium Dioxide and Titanium, and its effect on surface crack formation, will be elucidated. Parameter fitting, necessary for the implementation of tight binding and bond order potential methods, will be based on Bayesian Optimisation techniques. This will result in an acceleration of the fitting procedure and expansion of the simulations from a pure titanium medium, to an alloyed medium. Simulations of the alloyed system in a partial pressure environment will provide insight into how oxygen interacts and diffuses in/out of the material. The difference of dislocation propagation, interaction and pile up at the alloy/oxide interface will be accomplished. Distinctions between alloyed and pure Titanium mediums on crack morphology, formation and susceptibility will be drawn. Certain dislocation distributions/systems resulting from the machining and preparation of alloys will be linked to enhanced plasticity and fracture.

在钛/二氧化钛系统中，螺旋位错和刃位错的精确计算构造将通过利用“嵌入”的多尺度原子方法来实现：一种自洽的可极化离子紧密结合模型控制位错的非线性应力“核心”中的原子能量的技术，而键序势模型提供了一种更快但不太准确的方法 模拟原子能量——控制核心之外的原子区域。将研究间隙氧对位错动力学的影响，以及两种不同介质之间和内部的各种类型位错系统之间的相互作用。将阐明二氧化钛和钛之间的界面处位错堆积产生的增强应力场及其对表面裂纹形成的影响。实施紧密结合和键序势方法所必需的参数拟合将基于贝叶斯优化技术。这将导致拟合过程的加速以及模拟从纯钛介质扩展到合金介质的扩展。在分压环境中对合金系统进行模拟将深入了解氧气如何相互作用以及在材料中扩散。将实现合金/氧化物界面处位错传播、相互作用和堆积的差异。将得出合金和纯钛介质在裂纹形态、形成和敏感性方面的区别。合金加工和制备产生的某些位错分布/系统将与增强的塑性和断裂有关。