Glassy Ferromagnetic Shape Memory Alloys: Interplay Between Disorder, Phase Transitions, and Multi-Physics Couplings

非技术概述：形状记忆合金（SMA）是一种特殊类型的晶体金属，其可以在加热时恢复其变形形状，这是可逆的固体到固体结构相变（即马氏体相变）的结果。最近发现的SMA也是磁性的，并且表现出同时的马氏体和磁性转变。主要研究人员最近表明，仔细操纵这些合金中的缺陷可以带来新的玻璃样行为，其中“非晶”结构是根据磁自旋和/或应变定义的。这种多功能耦合、各种类型的固态的出现以及所产生的性质可以提供全新的功能，例如磁致动、有效的磁制冷、热管理、废机械能的收获以及经由远程致动的活性组织支架的细胞生长刺激。该奖项支持基础实验和理论研究和教育，以了解不同类型的固体到固体相变，玻璃化和晶体缺陷如何在磁性SMA中相互作用并影响其功能特性。这一新的认识有望对未来多功能智能材料的设计和开发产生积极影响。该奖项支持本科生和研究生在国家的最先进的实验和计算材料技术的培训。该项目的一个不可分割的方面是通过基于国家标准与技术研究所的材料数据固化System.Technical摘要：NiMnIn基磁性形状记忆合金（MSMAs）的材料数据库公开传播研究成果，该材料数据库表现出广泛的复杂现象，这些现象是由结构无序和不同类型的相变（有序、磁性、结构）之间的相互作用引起的，包括自旋玻璃和应变玻璃转变。这些相变导致涉及热、磁和机械热力学共轭对的多个耦合模式。反过来，合金表现出丰富的响应，导致独特的行为，如磁交换偏置，可剪裁的热膨胀，巨磁热和弹性热效应。主要研究人员已经表明，程度的秩序和点缺陷和反相边界的存在下，在控制多个竞争相的稳定性发挥了根本性的作用，但仍有很多未知的具体影响的配置无序的磁热机械性能的MSMA。在这个项目中的计算-实验相结合的方法的目标是阐明的机制和微观结构特征，确定不同的竞争相的稳定性，相变的发生和他们的耦合。重点是使用国家的最先进的多物理表征和建模，以调查的性质磁热机械耦合NiMnIn MSMAs作为配置顺序和各种外部刺激（温度，应力和磁场或其组合）的函数。结合第一性原理计算和Monte Carlo模拟，结合中子衍射测量的微结构和磁结构的原位调查被用来检查的磁结构相变和玻璃化行为的发病的配置无序的效果。该项目的主要科学影响预计将是发展健全的，基于多物理的合金化和热处理指南，用于调整磁性SMA中的磁性和结构响应。

NON-TECHNICAL SUMMARY:Shape Memory Alloys (SMAs) are a special type of crystalline metals that can recover their deformed shape upon heating, as a result of the reversible solid to solid structural phase transformations, i.e. martensitic transformations. Few recently discovered SMAs are also magnetic, and demonstrate simultaneous martensitic and magnetic transitions. The principal investigators have recently shown that careful manipulation of defects in these alloys can bring about novel glass-like behavior in which the 'amorphous' structure is defined in terms of magnetic spin and/or strain. Such multi-functional coupling, the appearance of various types of solid states, and the resulting properties may provide completely new functionalities such as magnetic actuation, efficient magnetic refrigeration, thermal management, harvesting of waste mechanical energy, and cell growth stimulation via remotely actuated active tissue scaffolds. This award supports fundamental experimental and theoretical research and education to understand how different types of solid to solid phase transformations, glassiness, and crystal defects interact in magnetic SMAs and influence their functional properties. The new understanding is expected to positively impact future design and development of multifunctional smart materials. The award supports the training of undergraduate and graduate students in state-of-the-art experimental and computational materials techniques. An integral aspect of this project is the open dissemination of research results through a Materials Data Repository based on the National Institute of Standards and Technology's Materials Data Curation System.TECHNICAL SUMMARY:NiMnIn-based Magnetic Shape Memory Alloys (MSMAs) exhibit a wide range of complex phenomena resulting from the interplay between configurational disorder and different types of phase transitions (ordering, magnetic, structural) including spin glass and strain glass transitions. These phase transitions result in multiple coupling modes involving thermal, magnetic and mechanical thermodynamic conjugate pairs. In turn, the alloys demonstrate rich responses that result in unique behavior such as magnetic exchange bias, tailorable thermal expansion, giant magneto-caloric and elasto-caloric effects. The principal investigators have shown that the degree of order and the presence of point defects and anti-phase boundaries play a fundamental role in controlling the stability of multiple competing phases but much remains unknown regarding the specific effect of configurational disorder on the magneto-thermo-mechanical properties of MSMAs. The goal of the combined computational-experimental approach in this project is to elucidate the mechanisms and microstructural features that determine the stability of the different competing phases, the onset of the phase transitions and their couplings. The focus is to use state-of-the-art multi-physics characterization and modeling to investigate the nature of magneto-thermo-mechanical couplings in NiMnIn MSMAs as a function of configurational order and various external stimuli (temperature, stress, and magnetic field or their combinations). In-situ investigation of micro and magneto structure coupled with neutron diffraction measurements in combination with first-principles calculations and Monte Carlo simulations are used to examine the effect of configurational disorder on the magneto-structural phase transitions and the onset of glassy behavior. The major scientific impact of this project is expected to be the development of sound, multi-physics-based alloying and heat treatment guidelines for tuning magnetic and structural responses in magnetic SMAs.