Extension of the 'five-parameter' grain boundary stereological method to textured alloys

将“五参数”晶界体视学方法扩展到织构合金

• 批准号: EP/F030819/1
• 负责人: Valerie Randle
• 金额: $ 11.26万
• 依托单位: Swansea University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FF030819%2F1
• 关键词: Extension; five; parameter; grain; boundary

Intergranular degradation such as corrosion can be a serious problem in many materials applications. Hence, it is of interest to study which grain boundary crystallographic parameters (i.e. boundary structure) are more resistant than others to this phenomenon. Recently it has become possible to use a stereological technique coupled with electron backscatter diffraction (EBSD) to measure all five grain boundary crystallographic parameters, i.e. both misorientation and boundary plane. This landmark experimental advance is delivering new insights into the link between grain boundary structure and properties. However, at present the 'five-parameter analysis' cannot be applied to materials which have a crystallographic texture, which includes many technologically important alloys.The first aim of this project is to remove that limitation. This will be achieved by the design and implementation of various multiple sectioning sampling routines (i.e. acquisition of EBSD maps from several non-parallel sectioning planes), in parallel with extensive revision of the existing software code to take into account non-random orientation distributions i.e. texture. Then the new scheme will be validated by application to alloys of the Al-Mg-Mn 5xxx series, which is being used to reduce mass in automotive chassis applications, and to commercially pure Ti. Focused ion beam (FIB) microscopy coupled with EBSD will be used to confirm and validate the procedures used. The data will provide information on the distribution of boundary planes, which is hitherto unknown in textured alloys, and will allow insights into the mechanism of texture formation. This information will then be applied to explore the relationship between boundary crystallography and intergranular corrosion in the Al-Mg-Mn alloys, which will in turn input to the larger initiative of reducing susceptibility of Al-Mg alloys to intergranular corrosion by proper control of the final gauge texture. This is a cost-effective project because the experimental work is well suited to be carried out by a research student and there are no equipment costs. The principal project partner is Professor Rohrer's group at Carnegie Mellon University, USA, where the five-parameter analysis was developed, and who will carry out the software revision. Other project partners are Hydro Aluminium, Germany, who have an interest in grain boundary network analysis in aluminium alloys and are providing specimens for the project, and the University of New South Wales, who are supporting the work with complementary FIB analysis. Extension of the five-parameter technique to textured materials would give it much more general applicability as a microstructural tool. Furthermore, given that mapping speeds by EBSD are now very rapid, it is envisaged that in the future five-parameter analysis could become incorporated into mainstream grain boundary analysis.

在许多材料应用中，晶间降解（如腐蚀）是一个严重的问题。因此，研究哪些晶界晶体学参数（即边界结构）比其他参数更能抵抗这种现象是很有意义的。近年来，结合电子背散射衍射（EBSD）的立体学技术已成为测量晶界五种晶体学参数（即取向偏差和晶界面）的可能。这一具有里程碑意义的实验进展为晶界结构和性质之间的联系提供了新的见解。然而，目前“五参数分析”还不能应用于具有晶体结构的材料，其中包括许多技术上重要的合金。这个项目的第一个目标就是消除这种限制。这将通过设计和实现各种多重切片采样例程（即从几个非平行切片平面获取EBSD地图）来实现，同时对现有软件代码进行广泛修订，以考虑非随机方向分布，即纹理。然后，新方案将通过Al-Mg-Mn 5xxx系列合金（用于减少汽车底盘应用中的质量）和商业纯Ti的应用来验证。聚焦离子束（FIB）显微镜结合EBSD将用于确认和验证所使用的程序。这些数据将提供有关边界面分布的信息，这是迄今为止在纹理合金中未知的，并将允许深入了解纹理形成的机制。这些信息将被应用于探索Al-Mg- mn合金中边界晶体学和晶间腐蚀之间的关系，进而通过适当控制最终规范织构来降低Al-Mg合金对晶间腐蚀的敏感性。这是一个具有成本效益的项目，因为实验工作非常适合由研究生进行，而且没有设备成本。项目的主要合作伙伴是美国卡耐基梅隆大学Rohrer教授的小组，该小组开发了五参数分析，并将进行软件修订。其他项目合作伙伴是德国的Hydro aluminum，他们对铝合金的晶界网络分析很感兴趣，并为该项目提供了样本，以及新南威尔士大学，他们通过补充FIB分析来支持这项工作。将五参数技术扩展到织构材料将使其作为微观结构工具具有更广泛的适用性。此外，鉴于目前EBSD的制图速度非常快，预计未来五参数分析可以被纳入主流的晶界分析。