Collaborative Research: Compositionally and Structurally Modulated Ferroelastic Films for Unprecedented Superelastic Properties

合作研究：成分和结构调制的铁弹性薄膜，具有前所未有的超弹性特性

• 批准号: 2333551
• 负责人: Yunzhi Wang
• 金额: $ 36.23万
• 依托单位: Ohio State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-02-01 至 2027-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2333551&HistoricalAwards=false
• 关键词: Collaborative; Research; Compositionally; Structurally; Modulated

NON-TECHNICAL SUMMARYMost metals and metallic alloys become permanently deformed even when they are stretched or compressed by a small amount (typically less than 1%). In contrast, a special category of materials known as Shape Memory Alloys (SMAs) can regain their original shape even after undergoing large deformations (up to 10%) once the loads are removed. This unique property of SMAs has led to a broad array of applications ranging from medical implants and robotics to flexible airplane wings and space exploration vehicle tires. However, the mechanical behavior of SMAs is highly non-linear, i.e., their deformation can increase drastically even for small changes in force, which can make them mechanically unstable. In addition, significant amounts of energy are wasted as heat when the SMAs recover their shape after being deformed. The primary goal of this integrated experimental and computational research project is to eliminate the undesirable mechanical instability and create SMAs that are more energy efficient. This is being accomplished by systematically modulating the chemical composition and structure of the SMAs at the nanoscale. This novel alloy design approach, termed as Nanoscale Compositional and/or Structural Modulation (NCSM), can be used to create not only mechanically stable and energy efficient SMAs but also other types of materials with highly tunable mechanical properties such as titanium-based alloys for bone implants that mimic the strength and stiffness of natural bones. The NSCM alloy design strategy, unique experimental processing and characterization techniques, and state-of-the-art computer simulation methodologies developed in this project are being broadly disseminated via conference talks, online tutorials, and articles in academic journals. The project is also advancing educational outreach and workforce development through hands-on demonstrations to high school students, recruitment of underrepresented minority students for conducting research and workforce training partnerships with regional community colleges and industries. TECHNICAL SUMMARYThe elastic strain limit of most metals and alloys is less than 0.5%, except for whiskers or freestanding nanowires. Ferroelastic materials such as shape memory alloys (SMAs), in contrast, can achieve giant recoverable strains of up to ~10%. However, the inherent nonlinearity of pseudo-elasticity in SMAs results in mechanical instability, characterized by strain avalanche driven stress plateaus and substantial stress-strain hysteresis. This integrated computational and experimental research project is addressing this pivotal issue by introducing an innovative approach, termed as Nanoscale Compositional and/or Structural Modulation (NCSM), to the design and synthesis of the next generation of SMAs. The NCSM concept capitalizes on the strong dependency of the critical stress for stress-induced martensitic transformation (MT) in NiTi SMAs on composition and grain size to eliminate strain avalanches during MT, and thus enable controlled strain release. The central hypothesis is that nanoscale modulations in chemical composition and microstructure will introduce confinements to the MT process, effectively suppress autocatalysis and fundamentally change the MT characteristics, leading to NiTi SMAs that are strong, linear superelastic, hysteresis-free, and have ultralow modulus. This hypothesis is being tested by synthesizing NCSM NiTi films with precisely defined nanoscale compositional and grain size modulations using physical vapor deposition, and characterizing their mechanical behavior using MEMS based tensile testing. The design of these NCSM NiTi films is being guided by computational modeling using molecular dynamics and phase field simulations. It is anticipated that this new class of NCSM SMAs can be designed to exhibit a wide array of highly tunable stress-strain behaviors that are desirable for a variety of advanced biomedical, functional, and structural applications. Although the focus of the project is on NiTi SMA, the NCSM alloy design concept is applicable to a broad class of materials for which structural phase transformations are utilized to tailor the properties.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术摘要大多数金属和金属合金即使在少量拉伸或压缩（通常小于 1%）时也会发生永久变形。相比之下，一类被称为形状记忆合金 (SMA) 的特殊材料即使在负载移除后发生较大变形（高达 10%）后也能恢复其原始形状。 SMA 的这种独特特性带来了广泛的应用，从医疗植入物和机器人到灵活的飞机机翼和太空探索车辆轮胎。然而，SMA 的机械行为是高度非线性的，即即使力发生微小变化，它们的变形也会急剧增加，这可能使它们机械不稳定。此外，当 SMA 变形后恢复形状时，大量能量会以热量的形式被浪费。这个综合实验和计算研究项目的主要目标是消除不良的机械不稳定性并创建更节能的 SMA。这是通过在纳米尺度上系统地调节 SMA 的化学成分和结构来实现的。这种新颖的合金设计方法被称为纳米级成分和/或结构调制（NCSM），不仅可用于制造机械稳定且节能的 SMA，还可用于制造具有高度可调机械性能的其他类型的材料，例如用于制造的钛基合金。模拟天然骨骼强度和刚度的骨植入物。该项目中开发的 NSCM 合金设计策略、独特的实验处理和表征技术以及最先进的计算机模拟方法正在通过会议演讲、在线教程和学术期刊上的文章广泛传播。该项目还通过向高中生进行实践示范、招募代表性不足的少数族裔学生进行研究以及与地区社区大学和行业建立劳动力培训伙伴关系来推进教育推广和劳动力发展。 技术概要 除晶须或独立式纳米线外，大多数金属和合金的弹性应变极限均小于 0.5%。相比之下，形状记忆合金 (SMA) 等铁弹性材料可以实现高达约 10% 的巨大可恢复应变。然而，SMA 中伪弹性固有的非线性会导致机械不稳定，其特征是应变雪崩驱动的应力平台和显着的应力应变滞后。这个综合计算和实验研究项目正在通过引入一种称为纳米级成分和/或结构调制（NCSM）的创新方法来解决这一关键问题，以设计和合成下一代 SMA。 NCSM 概念利用 NiTi SMA 中应力诱发马氏体相变 (MT) 的临界应力对成分和晶粒尺寸的强烈依赖性，消除 MT 期间的应变雪崩，从而实现受控应变释放。核心假设是，化学成分和微观结构的纳米级调节将对 MT 过程产生限制，有效抑制自催化并从根本上改变 MT 特性，从而产生坚固、线性超弹性、无滞后且具有超低模量的 NiTi SMA。这一假设正在通过使用物理气相沉积合成具有精确定义的纳米级成分和晶粒尺寸调制的 NCSM NiTi 薄膜进行测试，并使用基于 MEMS 的拉伸测试表征其机械行为。这些 NCSM NiTi 薄膜的设计以使用分子动力学和相场模拟的计算模型为指导。预计这种新型 NCSM SMA 可以设计成表现出各种高度可调的应力应变行为，这对于各种先进的生物医学、功能和结构应用来说是理想的。尽管该项目的重点是 NiTi SMA，但 NCSM 合金设计概念适用于利用结构相变来定制性能的广泛材料。该奖项反映了 NSF 的法定使命，并被认为值得通过以下方式获得支持：使用基金会的智力价值和更广泛的影响审查标准进行评估。