晶粒择优取向AlFe₂B₂合金的磁相变调控与反常热膨胀研究

Study on Manipulation of the Magnetic Phase Transition and Anomalous Thermal Expansion in Grain-Oriented AlFe₂B₂ Alloys

摘要: 负热膨胀具有控制和补偿正热膨胀的独特优势，是低温工程、航空航天、电子封装等领域的关键材料。然而，目前已知负热膨胀材料主要由重金属、稀土元素组成，由于密度大、成本高，所以限制了其实际运用。AlFe₂B₂合金由地球上丰富的、无毒轻质元素构成，是一种居里温度接近室温轻质磁相变合金。本研究利用定向凝固技术，在正交结构的AlFe₂B₂合金中制备了具有强织构的样品，并进一步通过Ge元素取代调控其磁性能和负热膨胀性能。借助扫描电子显微镜、X射线衍射仪、振动样品磁强计等仪器，本研究深入表征样品的显微形貌、晶体结构、磁相变行为以及负热膨胀性能。本研究获得的织构样品具有工作窗口覆盖室温(120-323 K)、大温域(∆T = 203 K)的优异性能，为新型轻质负热膨胀材料的应用提供了新的材料体系。

Abstract: Negative thermal expansion (NTE) exhibits unique advantages in the control and compensation of positive thermal expansion (PTE), making it highly applicable in cryogenic engineering, aerospace, and electronic packaging. However, current NTE materials primarily consist of heavy metals and rare earth elements, which are characterized by high density and cost, thereby restricting their practical utility. AlFe₂B₂ alloy, comprising abundant, non-toxic lightweight elements abundant on Earth, exhibits excellent magnetocaloric properties with a Curie temperature proximate to room temperature. The present work employed directional solidification techniques to fabricate samples with a pronouncedtexture in an ortho-rhombic AlFe₂B₂ alloy. Through the chemical substitution of Ge elements, the magnetic properties and negative thermal expansion performance were further modulated. The microstructure, crystal structure, magnetic phase transition behavior, and negative thermal expansion performance of the samples were comprehensively characterized using scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometry. The textured samples obtained in this study exhibited exceptional performance, demonstrating a working window spanning from room temperature (120-323 K) and a substantial temperature range (ΔT = 203 K). Consequently, this study introduces a new material family for the utilization of innovative lightweight negative thermal expansion materials.