Effect of crystallographic anisotropy and irradiation on fatigue and fracture of metals

真实的材料是高度各向异性的微晶的复杂的、不均匀的集合。它们的平均响应可以接近在实际应用中经常假设的各向同性行为。 然而，如果不考虑固有的不均匀行为，就无法理解许多反应。织构发展、耳环、晶间破坏、应力腐蚀开裂和许多其他效应不取决于平均应力，而是取决于局部行为和平均应力周围的应力分布。当这种材料受到循环载荷时，它们会发生不可逆的微观结构变化。 经过多次疲劳循环后，裂纹开始并通过试样传播，直到发生失效-这是研究计划的主题。* 除了常规技术（显微镜）外，还将使用一系列衍射技术来研究，例如，作为局部微观结构函数的能量储存/耗散以及微观结构对松弛/变形机制的影响。衍射可以揭示许多可能对疲劳行为产生影响的微观结构变化：晶粒之间和晶粒内的应力，以及变形引起的相变或晶粒旋转/重新取向。** 塑性的微观力学模型在预测简单加载条件下材料的响应方面非常成功。颗粒群的衍射监测是探索模型极限以及调整/验证它们的强大工具。我们将联合收割机实验衍射数据与多晶模型相结合，以探索局部性质对裂纹形成和生长方式的贡献。虽然温度和应力为研究提供了两个关键变量，但我们也将研究辐照。 由于高能粒子的存在，材料在辐射环境中的行为与传统应用中不同。 这些通过与原子的弹性碰撞引起原子位移，导致材料性质的显著变化。我们将使用加速器技术来模拟核反应堆内部或太空恶劣环境中的条件。 ** 来自实验和建模研究的信息将突出局部响应和原子尺度损伤对累积变形和能量储存以及裂纹扩展和应力消除的影响。它将提供微观机制对工程相关合金宏观行为的影响的理解，并将对包括发电，航空航天和汽车在内的一系列行业产生影响。这一建议将提供通过死后分析或常规实验根本无法获得的信息，开辟新的科学途径。它将在最先进的实验和建模技术方面对HQP进行培训。

Real materials are complex, inhomogeneous collections of highly anisotropic crystallites. Their mean response may approach the isotropic behaviour often assumed in practical applications.  However, many responses cannot be understood without accounting for the inherently inhomogeneous behaviour. Texture development, earring, intergranular failure, stress corrosion cracking and many other effects are dependent not on average stress, but rather on the local behaviour and the distribution of stresses around the average. When such materials are subjected to cyclic loading, they undergo irreversible microstructural change. After a number of fatigue cycles, cracks initiate and propagate through the specimen until failure occurs - this is the topic of the research program. ***As well as conventional techniques (microscopy) a range of diffraction techniques will be used to study, e.g. energy storage / dissipation as a function of local microstructure and the influence of microstructure on relaxation / deformation mechanisms. Diffraction can reveal many microstructural changes which are likely to have an influence on fatigue behaviour: the stress both between and within grains, and deformation-induced phase transformations or grain rotation/reorientation. ******Micromechanical models of plasticity have been highly successful in predicting the response of materials under simple loading conditions. Diffraction monitoring of grain populations is a powerful tool in exploring model limits, as well as tuning / validating them. We will combine experimental diffraction data with polycrystalline models to explore the contributions of local properties to the way that cracks form and grow.******While temperature and stress provide two key variables for investigation, we will also investigate irradiation. Materials behave differently in a radiation environment than in conventional applications due to the presence of high energy particles. These cause atomic displacements by elastic collision with atoms, resulting in significant changes in material properties. We will use accelerator technology to simulate the conditions which can be found inside a nuclear reactor or in the hostile environment of space. ******The information from the combined experimental and modeling studies will highlight the influence of local response and atomic scale damage on accumulated deformation and energy storage as well as crack propagation and stress relief. It will provide an understanding of the influence of microscopic mechanisms on macroscale behaviour of engineering relevant alloys, and will have an impact on a range of industries including power generation, aerospace and automotive. This proposal will provide information that is simply not available through post-mortem analysis or conventional experiments, opening up new avenues of science. It will train HQP in state of the art experimental and modelling techniques.**