Investigation of the Roles of Strain Rate and Twinning in the High Ductility of B2 Intermetallic Compounds

应变率和孪生在 B2 金属间化合物高延展性中的作用研究

• 批准号: 0413616
• 负责人: Alan Russell
• 金额: $ 28万
• 依托单位: Iowa State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-08-15 至 2008-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0413616&HistoricalAwards=false
• 关键词: Investigation; Roles; Strain; Rate; Twinning

This award by the Division of Materials Research to Iowa State University is to test two theories that attempt to explain the high ductility of the RM intermetallics, where R is a rare earth metal and M is a metal from Groups 2, 8-13. The chemical, physical, magnetic, and mechanical properties of intermetallic compounds are often superior to those of other metals, but enormous potential of intermetallics to improve engineering performance remains underutilized because they are brittle and fracture easily at room temperature. Recently there has been the discovery of high ductility and high fracture toughness at room temperature in fully ordered, stoichiometric B2 intermetallic RM compounds, This research project explores two theories that might explain the high ductility of the RM intermetallic compounds. One theory attributes the high ductility to grain boundary effects. Arc-melted and hot rolled RM alloys studied to date form with average grain sizes of about 0.2 mm. Strain rate sensitivity will be measured by tensile "jump tests" to determine whether phenomena such as grain boundary sliding contribute to the ductility. Tensile tests will be performed at cryogenic and elevated temperatures. The second theory attributes the high ductility to twinning effects. Preliminary studies show indications of twinning in single crystal RM intermetallics. Transmission electron microscopy (TEM) of deformed RM specimens will be used to search for twins. If twins are found, TEM will determine twinning planes and shear directions. These findings will either support or refute each of the two theories. With the basic mechanism of ductility established, the performance of new RM intermetallics can then be hypothesized, guiding future alloy development.There are approximately 130 RM intermetallics prepared from a rare earth metal R and a metal (M) from Groups 2, 8-13, and some of these intermetallics have potential use in engineering structural applications. A few RM intermetallics have low densities or possess high oxidation resistance, suggesting possible applications in aerospace structures and turbomachinery. Other RM intermetallics have interesting magnetic and magnetocaloric behavior. Room temperature ductility and high fracture toughness would aid fabrication of these alloys and improve performance. However, the greatest value of studying the RM compounds could lie in advancing the understanding of the factors facilitating their plasticity. Insights gained from this study will be helpful in guiding future efforts to improve the ductility of other intermetallic compounds. The research involves both graduate and undergraduate students.

爱荷华州立大学材料研究部的这一奖项是测试两种试图解释RM Interallalsics高延展性的理论，其中R是一种稀土金属，M是第2组，8-13组的金属。金属间化合物的化学，物理，磁性和机械性能通常优于其他金属的化学性能，但是金属间的化学化合物的改善工程性能的巨大潜力仍然不足，因为它们在室温下容易易碎且裂缝。最近，在室温下发现了高延展性和高骨折韧性，该研究项目探讨了两种可能解释RM金属间化合物的高延展性的理论。一种理论将高延展性归因于晶界影响。弧线融化和热卷的RM合金迄今为止的形式，平均晶粒尺寸约为0.2 mm。应变速率灵敏度将通过拉伸“跳跃测试”来测量，以确定诸如晶界滑动之类的现象是否有助于延展性。拉伸测试将在低温和升高的温度下进行。第二个理论将高延展性归因于孪生效应。初步研究表明，单晶RM金属间的孪生指示。变形RM样品的透射电子显微镜（TEM）将用于寻找双胞胎。如果发现双胞胎，TEM将确定双平面和剪切方向。这些发现将支持或反驳这两种理论中的每一个。借助建立延展性的基本机制，可以假设新的RM金属金属质量的性能，从而指导未来的合金开发。大约有130 RM从稀土金属R和第2组，8-13的金属R和金属（M）制备的金属间代理，其中一些金属金属在工程结构应用中具有潜在的用途。一些RM的金属间代理具有低密度或具有较高的氧化耐药性，这表明可能在航空航天结构和涡轮机械中使用。其他RM金属间学具有有趣的磁性和磁性行为。室温延展性和高断裂韧性将有助于制造这些合金并提高性能。但是，研究RM化合物的最大价值可能在于促进对促进其可塑性因素的理解。从这项研究中获得的见解将有助于指导未来的努力，以改善其他金属间化合物的延展性。该研究涉及研究生和本科生。