发表机构
Helmholtz-Zentrum Dresden-Rossendorf; Würzburg-Dresden Cluster of Excellence ctd.qmat; Leibniz Institute for Solid State and Materials Research Dresden; Technische Universität Bergakademie Freiberg; Technical University of Darmstadt; Institut für Festkörper- und Materialphysik, Technische Universität Dresden（德累斯顿-罗森多夫赫尔霍兹中心; 维尔茨堡-德累斯顿卓越集群ctd.qmat; 德累斯顿莱布尼茨固态与材料研究所; 弗莱贝格矿业技术大学; 达姆施塔特工业大学; 德累斯顿工业大学固体与材料物理研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究提出粉末装管约束作为抗疲劳热卡材料的设计原则，通过钢套约束脆性Heusler合金粉末，实现高耐久性并开发原位测量技术解析相变行为。
AI 中文摘要
热卡固态制冷为蒸汽压缩制冷提供了一种节能替代方案，但许多最有前景的材料，包括磁热和弹热Heusler合金，本质上易碎，在运行所需的循环载荷下会发生失效。在此，我们通过粉末装管（PIT）工艺引入机械约束，作为克服这一局限的通用策略。通过将87%堆积密度的粒状Heusler合金芯嵌入韧性钢套（外径2.8毫米，壁厚0.3毫米）中，该复合材料约束了脆性粉末，并实现了颗粒间的有效载荷传递。虽然芯部本质上仍是脆性的，但周围的套筒防止了灾难性碎裂，将脆性从一种不合格的特性转变为可控的特性。我们证明，这种方法将机械耐久性提高了数个数量级，复合材料在250兆帕下承受了100,000次载荷循环而无结构失效，并耐受高达700兆帕的过载应力。约束还改变了相变本身，为了解析这些机械复杂系统中的这种行为，我们开发了一种同时原位测量技术，在载荷下结合应变和交流磁化率。该技术揭示，芯部的内应力场是强烈非均匀的。因此，宏观应变与相变相分数脱钩，马氏体转变无法仅通过机械数据追踪。因此，机械约束成为抗疲劳热卡材料的设计原则，而结合的原位方法成为复合材料、多孔材料及其他机械非均匀热卡系统的表征工具。
英文摘要
Caloric solid-state refrigeration offers an energy-efficient alternative to vapor-compression cooling, but many of the most promising materials, including the magneto- and elastocaloric Heusler alloys, are intrinsically brittle and fail under the cyclic loading required in operation. Here, we introduce mechanical confinement via powder-in-tube (PIT) processing as a general strategy to overcome this limitation. By embedding a granular Heusler alloy core of 87 % packing density within a ductile steel sheath (2.8 mm outer diameter, 0.3 mm wall thickness), the composite confines the brittle powder and enables effective load transfer between particles. While the core remains inherently brittle, the surrounding sheath prevents catastrophic fragmentation and turns brittleness from a disqualifying property into a manageable one. We demonstrate that this approach enhances mechanical durability by several orders of magnitude, with the composites sustaining 100,000 load cycles at 250 MPa without structural failure and tolerating overload stresses up to 700 MPa. Confinement also alters the transformation itself, and to resolve this behavior in these mechanically complex systems, we developed a simultaneous in-situ measurement technique combining strain and AC magnetic susceptibility under load. It reveals that the internal stress field in the core is strongly heterogeneous. As a consequence, the macroscopic strain decouples from the transforming phase fraction, and the martensitic transition cannot be tracked by mechanical data alone. Mechanical confinement thus emerges as a design principle for fatigue-resistant caloric materials, and the combined in-situ method as a characterization tool for composite, porous, and other mechanically heterogeneous caloric systems.
