Atomic Level Study of Grain Boundary Diffusion in Intermetallic Compounds using Polysynthetically Twinned TiAl as a Model System

使用多合成孪晶 TiAl 作为模型系统的金属间化合物晶界扩散的原子水平研究

• 批准号: 9615228
• 负责人: David Luzzi
• 金额: $ 50.04万
• 依托单位: University of Pennsylvania
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-06-01 至 2002-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9615228&HistoricalAwards=false
• 关键词: Atomic; Level; Study; Grain; Boundary

9615228 Luzzi An opportunity exists to carry out a basic investigation of the relationship between interfacial structure and diffusion along interfaces in intermetallic alloys. The crystallographically sharp twin-like and fault interfaces found in the lamellar structure of the technologically important intermetallic compound TiAl provide a model system which is ideal for such a study. The structure of the interfaces in this alloy system allow high-resolution electron microscopy (HREM) analysis to be used to study the location of atoms. Together with high resolution compositional analysis, electron energy loss spectroscopy, and theoretical atomistic modeling, the location of solute atoms on well-characterized interfaces in TiAl are determined. Large crystals of the lamellar TiAl are grown by optical float zone processing. High temperature Rutherford backscattering spectroscopy experiments measure the time for penetration of the solute atoms along the interfaces at various temperatures through a thin film. Incorporation of the results of the HREM analysis allows the interface diffusion coefficients and activation energies to be calculated via a Hwang-Balluffi analysis as a function of interface structure and diffusion direction. Theoretical studies are tied to the experimental program through the determination of minimum energy interfacial structures by molecular statics calculations employing potentials that include the directional character of bonding in TiAl. An important aspect of the theoretical studies is the development of these potentials. The diffusion properties at the interface are investigated through a detailed analysis of vacancy configurations within and near the interfaces and vacancy migration energies. The results of this theoretical analysis are correlated with the experimental measurements to develop a clearer understanding of the atomic level diffusion processes on interfaces. This research program which combines synergistic expe rimental and theoretical studies provides an excellent vehicle for graduate education in which the students will be immersed in in-depth experimental or theoretical investigations and will be continuously exposed to the complementary approach. %%% Intermetallic alloys are candidate materials for high temperature applications where stability of structure is important. This research should provide increased understanding of the influence of structure on diffusion of alloying elements. ***

9615228 Luzzi 有机会对金属间合金中界面结构和沿界面扩散之间的关系进行基本研究。 在技​​术上重要的金属间化合物 TiAl 的层状结构中发现的晶体学上尖锐的孪晶界面和断层界面为此类研究提供了理想的模型系统。 该合金系统中的界面结构允许使用高分辨率电子显微镜（HREM）分析来研究原子的位置。 结合高分辨率成分分析、电子能量损失光谱和理论原子建模，确定了 TiAl 中特征良好的界面上溶质原子的位置。 层状 TiAl 的大晶体通过光学浮区处理生长。 高温卢瑟福背散射光谱实验测量溶质原子在不同温度下沿界面渗透穿过薄膜的时间。 结合 HREM 分析的结果，可以通过 Hwang-Balluffi 分析计算界面扩散系数和活化能，作为界面结构和扩散方向的函数。 理论研究与实验程序联系在一起，通过使用包括 TiAl 中键合方向特征的电势进行分子静力学计算来确定最小能量界面结构。 理论研究的一个重要方面是这些潜力的开发。 通过详细分析界面内和界面附近的空位构型以及空位迁移能量来研究界面处的扩散特性。 该理论分析的结果与实验测量相关联，以便更清楚地了解界面上的原子级扩散过程。 该研究计划结合了协同实验和理论研究，为研究生教育提供了一个极好的工具，学生将沉浸在深入的实验或理论研究中，并不断接触补充方法。 %%% 金属间合金是结构稳定性非常重要的高温应用的候选材料。 这项研究应该可以加深人们对结构对合金元素扩散影响的理解。 ***