低滞后巨弹热磁性形状记忆合金的设计研究

Driven by external fields, lattice vibration in solid-state phase transition materials always leads to the abrupt changes in physical behaviors. The significant application of giant magnetic-, elastic- and electric-caloric effects is the energy-efficient and environmentally friendly solid-state refrigeration technologies. Among them, elastocaloric cooling stems from large entropy change in stress-induced martensitic transformation has become one important potential to replace conventional vapor-compression method. However, the relatively large thermal/mechanical hysteresis, insufficient latent heat and high driven stress seriously limit the further development of elastocaloric cooling. In this context, this proposal aims to carry out the present work to solve these drawbacks by using various approaches, such as lattice design principle, oriented crystal growth technology and stress-magnetic field coupling effect. We hope to (i) achieve low hysteresis and high reversibility in series of Magnetic Shape Memory Alloys (MSMAs) undergoing large first-order phase transformation by tuning lattice parameters based on the Cofactor Conditions, i.e. kinematic conditions of compatibility between phases; (ii) enhance the elastocaloric effect in MSMAs by multi-fields coupling approach, i.e. driving the phase transformation by thermomechanical and magnetomechanical coupled loadings; (iii) demonstrate the energy conversion by elastocaloric effect and characterize the performance parameters such as latent heat, superelastic strain, work output per cycle and mechanical cycling fatigue; (iv) reveal the microstructure-property relationship for the low-hysteresis MSMAs showing giant elastocaloric effect. With the framework of this project, it would be expected to form a complete design chain for exploring the reversible elastocaloric materials by multifield application, to establish the evaluation standard of elastocaloric effect, and to provide the scientific base for the development of elastocaloric cooling technique.

固态相变材料在外场激励下，微观尺度的晶格微调会导致宏观尺度的物理特性突变，其中巨熵变材料的突出应用是节能环保的固态制冷技术。利用机械外力对马氏体相变合金加热和冷却的弹热制冷已成为最有潜力的固态制冷技术，但相变滞后大、潜热较低、驱动场高是弹热材料的最大缺陷。本项目以Ni基Heusler型磁性形状记忆合金为研究对象，通过相变晶体学理论，取向晶体生长技术和多场相变耦合手段，直接设计晶格结构参数和相变对称性，最大化提高相变材料热效应，降低相变外场强度和滞后损耗，开发兼具高效能量转化能力和抗机械疲劳能力的磁性弹热材料。最终形成基于多场可逆相变的弹热材料开发的完整设计链，给出性能评估体系标准，为发展弹热制冷技术的安全服役提供科学基础。

基于磁相变热效应的固态制冷是利用外加场驱动相变产生潜热从而实现制冷的技术，无环境污染、理论效率高, 被认为是最有希望替代当前主流气体压缩制冷的技术。本项目按照资助计划书所述开展相关研究内容，以Ni基Heusler型磁性形状记忆合金为对象，开展相变晶体学理论、取向晶体生长技术和多场相变耦合研究，建立了相变熵变与磁弹耦合强度之间的朗道量化模型，开发了在12000循环过程中获得了可逆的弹热绝热温变11K的NiFeGaCo单晶，设计出韧性相增强力学性能良好的NiMnSnCo合金弹热双相材料，采用定向凝固制备高度取向的NiCoMnTi多晶，将相变临界应力从350MPa降低至50MPa，揭示了多重调制马氏体的良好自适应性和高取向晶粒之间的协调变形对低相变滞后的影响机理，因此对发展兼具高效能量转化能力和抗机械疲劳能力的磁性弹热材料具有较强的理论和技术意义。在项目资助下，共发表学术论文12篇。申请专利3件，授权3件。培养博士研究生4名，硕士研究生4名。