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

形状记忆合金（sma）是一种特殊类型的晶体金属，由于可逆的固体到固体的结构相变，即马氏体相变，加热后可以恢复其变形的形状。最近发现的一些sma也是磁性的，并且同时表现出马氏体和磁性转变。首席研究人员最近表明，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/或应变来定义的。这种多功能耦合，各种固态的出现，以及由此产生的特性可能提供全新的功能，如磁驱动，高效磁制冷，热管理，废机械能的收集，以及通过远程驱动的活性组织支架刺激细胞生长。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相转变，玻璃性和晶体缺陷如何在磁性sma中相互作用并影响其功能特性。新的认识有望对多功能智能材料的未来设计和开发产生积极影响。该奖项支持本科生和研究生在最先进的实验和计算材料技术方面的培训。该项目的一个组成部分是通过基于美国国家标准与技术研究所材料数据管理系统的材料数据存储库公开传播研究成果。技术概述：基于nimni的磁性形状记忆合金（msma）表现出广泛的复杂现象，这些现象是由构型无序和不同类型的相变（有序、磁性、结构）（包括自旋玻璃和应变玻璃转变）之间的相互作用造成的。这些相变导致了多种耦合模式，包括热、磁和机械热力学共轭对。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，可定制的热膨胀，巨大的磁热效应和弹性热效应。主要研究人员已经表明，有序程度和点缺陷和反相边界的存在在控制多个竞争相的稳定性方面起着基本作用，但关于构型无序对msma磁热机械性能的具体影响仍不清楚。在这个项目中，计算与实验相结合的方法的目标是阐明决定不同竞争相稳定性的机制和微观结构特征，相变的开始和它们的耦合。重点是使用最先进的多物理表征和建模来研究NiMnIn msma中磁-热-机械耦合的性质，作为结构顺序和各种外部刺激（温度，应力和磁场或它们的组合）的函数。采用原位微磁结构研究、中子衍射测量、第一性原理计算和蒙特卡罗模拟相结合的方法，研究了构型无序对磁结构相变和玻璃化行为的影响。预计该项目的主要科学影响将是为磁性sma的磁性和结构响应调谐制定健全的、基于多物理场的合金化和热处理指南。

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.