A Study of Massive and other Phase Transformations in TiAl- Based Intermetallic Alloys

TiAl基金属间合金中大量相变和其他相变的研究

• 批准号: 9731349
• 负责人: Vijay Vasudevan
• 金额: $ 28.25万
• 依托单位: University of Cincinnati Main Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-07-15 至 2002-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9731349&HistoricalAwards=false
• 关键词: Study; Massive; other; Phase; Transformations

9731349 Vasudevan This research applies high resolution transmission electron microscopy in a study of the massive transformation in TiAl- based intermetallic alloys. Two important issues are addressed related to the mechanisms of massive transformations in TiAl alloys: (1) the nature of the massive -parent interphase interfacial structure, and (2) the role of defect structures. The study focuses on alloys with aluminum contents between 46-47 at. %, which allows retention of large areas of the massive-parent interfaces. Orientation relationships that develop during nucleation and the early stages of growth of the massive phase are studied in samples whose reaction kinetics has been determined. The structures of the parent -massive phases and the types of interfaces that between them are determined in samples undergoing different undercoolings, reaction start temperatures, and growth rates. The state of coherency of the interfaces is determined and from these studies atomistic models of the structures of the massive-parent interphase interfaces are developed. The atomic structures of defects (dislocations and stacking faults) are determined as well, and their role in the growth of the massive product assessed. %%% New alloys based on the TiAl compound are of great importance for application in high temperature propulsion systems because of their unique combination of properties. Mechanical properties of these materials are controlled by their microstructures, which is the focus of this research. ***

9731349本研究应用高分辨率电子显微镜研究TiAl基金属间化合物合金的块状相变。讨论了与TiAl合金块状相变机制有关的两个重要问题：(1)块状母相界面结构的性质；(2)缺陷结构的作用。这项研究的重点是铝含量在46-47at之间的合金。%，这允许保留大量父接口的较大区域。在已确定反应动力学的样品中，研究了在形核和块体相生长的早期阶段发展的取向关系。在经历不同过冷度、反应起始温度和生长速率的样品中，确定了母体-块体相的结构和它们之间的界面类型。确定了界面的共格状态，并从这些研究中建立了块状母体界面结构的原子模型。还确定了缺陷(位错和层错)的原子结构，并评估了它们在大量产品生长中的作用。基于TiAl化合物的新型合金由于其独特的性能组合，在高温推进系统中的应用具有重要意义。这些材料的力学性能受其微观组织的控制，这是本研究的重点。***