Collaborative Research: deformation mechanisms of fcc and hcp Cobalt with high-density stacking faults

合作研究：具有高密度堆垛层错的fcc和hcp钴的变形机制

• 批准号: 1642759
• 负责人: Xinghang Zhang
• 金额: $ 24.87万
• 依托单位: Purdue University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-05-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1642759&HistoricalAwards=false
• 关键词: Collaborative; Research; deformation; mechanisms; fcc

Nontechnical summary:Cobalt (Co), in the form of thin films, is a critical magnetic material with widespread applications in magnetic data storage devices, microelectromechanical and nanoelectromechanical systems (MEMS/NEMS), as well as environmentally benign wear and corrosion resistant coatings. Yet, the mechanical properties of Co films, either in face-centered-cubic (fcc) or hexagonal-close-packed (hcp) form are poorly understood. The principal investigator's recent studies show that high-density stacking faults (SFs) - atomic planes that disrupt the ordered arrangement of atoms - can be introduced into fcc and hcp Co. These SFs may drastically enhance mechanical properties leading to higher strength and ductility of Co. The aim of the project is to elucidate the effect of the density of SFs and systematically investigate the mechanical properties of Co with SFs. The investigators have existing collaborations and their expertise nicely complements each other. The collaboration provides students with the opportunity to gain complementary knowledge in experiments and simulations through mutual visits, lectures and seminars at the participating institutions. The investigators also have arrangement for graduate students to visit the Department of Energy - Center for Integrated Nanotechnologies to access advanced microscopy facilities. The knowledge derived from this project can be incorporated into curricula at both institutions. The co-investigator can leverage successful outreach programs at University of Houston to broaden participation in engineering. The principal investigator can recruit a minority graduate student through the "Pathway to Doctoral Program" from minority institutions. Both investigators continuously supervise undergraduate students and encourage their students to attend major conferences. Technical summary:The objective of this project is to investigate the deformation mechanisms in fcc and hcp Co with high-density SFs. The ultimate goal is to understand the significance of SFs in governing the mechanical properties of metals, and improving the strength and deformability of Co. The investigators combine experiments and molecular dynamics simulations to perform the following major tasks: (1) understand the nucleation of SFs and the formation of intercepted SFs in fcc Co, and tailor the density of SFs in fcc and hcp Co; 2) examine the deformation mechanisms in fcc Co, including dislocation-SF interactions, size effect and work hardening, via a combination of in situ nanoindentation and atomistic modeling; and 3) investigate the deformation mechanisms in hcp Co with high density SFs and understand nucleation mechanisms of deformation twins in hcp Co. This project could reveal the significant role of SFs in mechanical behavior of metals. Furthermore, the combination of novel nanomechanical testing tools with molecular dynamics simulations fills in the knowledge gap through comprehensive interrogation of the deformation mechanisms in fcc and hcp Co with SFs at the atomistic level.

非技术摘要：薄膜形式的钴（Co）是一种关键的磁性材料，广泛应用于磁性数据存储器件、微机电和纳米机电系统（MEMS/NEMS）以及环境友好型耐磨和耐腐蚀涂层。然而，对于面心立方 (fcc) 或六方密堆积 (hcp) 形式的钴薄膜的机械性能知之甚少。首席研究员最近的研究表明，高密度堆垛层错 (SF)（破坏原子有序排列的原子平面）可以引入 fcc 和 hcp Co 中。这些 SF 可以大大增强机械性能，从而提高 Co 的强度和延展性。该项目的目的是阐明 SF 密度的影响，并系统地研究 Co 与 SF 的机械性能。研究人员已有合作，他们的专业知识可以很好地互补。此次合作为学生提供了通过参与机构的互访、讲座和研讨会获得实验和模拟方面的互补知识的机会。研究人员还安排研究生参观能源部集成纳米技术中心，以使用先进的显微镜设施。从该项目中获得的知识可以纳入两个机构的课程中。联合研究者可以利用休斯顿大学成功的外展项目来扩大工程领域的参与。首席研究员可以通过“博士通道”从少数民族院校招收少数民族研究生。两位研究人员不断监督本科生并鼓励他们的学生参加主要会议。 技术摘要：该项目的目的是研究具有高密度SFs的fcc和hcp Co的变形机制。最终目标是了解SFs在控制金属力学性能、提高Co的强度和变形能力方面的重要性。研究人员结合实验和分子动力学模拟来执行以下主要任务：（1）了解SFs的成核作用以及 fcc Co 中截获 SF 的形成，并调整 fcc 和 hcp Co 中 SF 的密度； 2) 通过原位纳米压痕和原子建模相结合，研究 fcc Co 的变形机制，包括位错-SF 相互作用、尺寸效应和加工硬化； 3）研究具有高密度SFs的hcp Co的变形机制，并了解hcp Co中形变孪晶的成核机制。该项目可以揭示SFs在金属机械行为中的重要作用。此外，新颖的纳米力学测试工具与分子动力学模拟相结合，通过在原子水平上全面探究 fcc 和 hcp Co 与 SF 的变形机制，填补了知识空白。