Thermal Stabilization and Mechanical Properties of Nanocrystalline Fe-Cr-Ni Alloys

纳米晶 Fe-Cr-Ni 合金的热稳定性和力学性能

• 批准号: 1005677
• 负责人: Ronald Scattergood
• 金额: $ 43.5万
• 依托单位: North Carolina State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-08-15 至 2013-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1005677&HistoricalAwards=false
• 关键词: Thermal; Stabilization; Mechanical; Properties; Nanocrystalline

TECHNICAL SUMMARY: It has been proposed that small additions of appropriate alloying elements (dopants) can stabilize a nanocrystalline grain size to high temperatures by means of a thermodynamic mechanism. The concept is based on the idea that solute segregation to grain boundaries can reduce the effective grain boundary energy to zero. Hence the driving force for grain growth is eliminated. Alloy additions of carefully selected solutes that segregate to grain boundaries in Fe-Ni-Cr alloys will be used in conjunction with ball milling to produce nanocrystalline alloys in powder form. Short term annealing with suitable microstructure characterization will be done to identify a regime of temperatures where the alloy powders can be consolidated by hot compaction without grain growth. An initial evaluation of the strength and ductility properties will follow. Investigation of the grain growth mechanisms that govern long-term thermal stability will be accomplished by a comprehensive and fundamental approach. The annealing kinetics and microstructure evolution will be determined using isothermal annealing experiments, with microstructure characterization techniques that have resolution down to the atomic scale, so that mechanisms can be identified and model-based extrapolations can be developed to verify long-term stability. The modeling results will be used to tailor Fe-Ni-Cr nanocrystalline alloys for optimum combinations of thermal stability, high strength and good tensile ductility.NON-TECHNICAL SUMMARY: The strength of metals can be increased to very high levels if the grain size is reduced to nanometers. However, these nanocrystalline metals are normally unstable at elevated temperature because the grains grow in size and the strength is lost. The proposed research will produce new nanocrystalline steels and stainless steels (Fe-Ni-Cr alloys) that have very high strength and the grain size is stable at high temperatures. These materials can be used to improve the efficiency of power generation systems, engines, and other applications where high strength-to-weight ratios and elevated temperature performance are required. An equally important aspect of the research is the development of intellectual resources in the form of science and engineering graduates who can develop new technology and transfer that knowledge to US industry.

技术概要：已经提出，少量添加适当的合金元素（掺杂剂）可以通过热力学机制使纳米晶晶粒尺寸稳定到高温。该概念基于溶质向晶界偏聚可以将有效晶界能降低到零的想法。因此，消除了晶粒生长的驱动力。合金添加剂将与球磨结合使用，以产生粉末形式的纳米晶合金，所述合金添加剂是精心选择的溶质，其在Fe-Ni-Cr合金中偏析到晶界。将进行具有合适的微观结构表征的短期退火，以确定合金粉末可以通过热压制而不发生晶粒生长的温度范围。随后将对强度和延展性进行初步评估。研究的晶粒生长机制，管理长期的热稳定性将完成一个全面的和基本的方法。退火动力学和微观结构演变将使用等温退火实验来确定，其中微观结构表征技术的分辨率可达原子尺度，以便可以识别机制并开发基于模型的外推来验证长期稳定性。模拟结果将用于定制Fe-Ni-Cr纳米晶合金，以实现热稳定性、高强度和良好拉伸延展性的最佳组合。非技术总结：如果晶粒尺寸减小到纳米，金属的强度可以提高到非常高的水平。然而，这些纳米晶体金属通常在高温下不稳定，因为晶粒尺寸增大并且强度损失。拟议的研究将生产新的纳米晶钢和不锈钢（Fe-Ni-Cr合金），这些钢具有非常高的强度，并且在高温下晶粒尺寸稳定。这些材料可用于提高发电系统、发动机和其他需要高强度重量比和高温性能的应用的效率。研究的一个同样重要的方面是以科学和工程毕业生的形式开发智力资源，他们可以开发新技术并将这些知识转移到美国工业。