磁性合金中的“磁有序强化”现象及其机理探索

Strengthening of metallic materials for high temperature is always attractive and a challenge for researchers in material sciences. Those conventional methods to strengthen metallic materials, for example, second phase strengthening, used to deteriorate the materials due to their insufficient thermal stability at elevated temperatures. Therefore, according to the phenomenon of high temperature magnetic ordering strengthening mentioned lately, the feasibility is to be systematically discussed for it to strengthen the high temperature structural materials and improve their creep performances. In the present study, high temperature creep and tensile tests will be conducted to investigate the phenomenon of high temperature magnetic ordering strengthening under the steady state and dynamic loadings for different Fe-based binary alloys with high Curie temperature. By means of differential scanning calorimetry (DSC),X-ray diffraction (XRD), vibrating sample magnetometer(VSM), M?ssbauer spectroscopy(MS), scanning electronic microscopy（SEM）, electron backscattered diffraction（EBSD）, high resolution transmission electron microscopy (HR-TEM) and magnetic force microscopy(MFM), ferromagnetic-paramagnetic phase transition is to be studied for Fe-based alloys with different contents and under different temperatures, and variations of magnetic ordering and magnetic domain in them is to be analyzed. Interactions of crystal defects and magnetic domain during plastic deformation will be determined, and the effects of content and temperature on magnetic ordering strengthening will be discussed. According to experimental results and theoretical analyses, the mechanism of magnetic ordering strengthening for Fe-based alloys is to be clarified on a micro-scale. Concerned with the present study, it is expected to provide some theoretical knowledge based on the magnetic ordering strengthening, and to essentially guide the designing, development and engineering applications for high temperature metallic materials.

高温金属材料的强化问题一直都是材料研究领域的热点与难点。常规的强化方式（如第二相强化等）在较高温度下因热力学稳定性不足加速材料的失效。本项目根据新发现的"高温磁有序强化"现象，系统探讨其作为高温结构材料强化方式和提升蠕变性能的可行性。 本申请拟以具有磁有序强化特征的高居里温度Fe基合金为研究对象，通过高温蠕变和高温拉伸试验，研究静态和动态载荷下不同组分铁基合金在高温下的磁有序强化现象。利用DSC、XRD、VSM、MS、SEM、EBSD、HR-TEM、MFM等表征手段，研究不同成分和温度下Fe基合金磁有序相变转变规律，分析Fe基合金中磁有序度和磁畴的变化，揭示塑性变形过程中晶体缺陷与磁畴的交互作用，探讨成分和温度对磁有序强化的影响规律，从微观层面阐明Fe基合金中磁有序强化的机理。本项目的完成可为磁有序强化方式提供一定的理论基础，对于高温金属材料的设计、开发及工程应用具有重要的理论指导。

高温金属材料的强化问题一直都是材料研究领域的热点与难点。常规的强化方式在较高温度下因低的热力学稳定性加速材料的失效,“高温磁有序强化”是可能弥补高温强度不足的一种新强化方式。.为此，本项目以具有磁有序强化特征的高居里温度Fe基合金为研究对象，通过高温蠕变和高温拉伸试验，研究了静态和动态载荷下不同组分铁基合金在高温下的磁有序强化现象，考察了变形条件下Fe基合金中磁矩取向分布的变化对磁畴偏转及磁畴结构间转化的影响，分析了变形条件与磁畴组织的内在关系，解析了不同变形条件下Fe基合金中位错缺陷的运动机制及其与磁畴的交互作用，从微观层面揭示了“磁有序强化”的本质。研究了不同组分Fe基合金铁磁－顺磁转变的相变规律，分析了Fe基合金固溶体中原子磁矩大小的变化，探究了Fe基合金中磁畴大小、分布和磁畴结构变化的影响规律，考察了磁畴界壁的移动行为及畴壁移动过程中磁矩和磁有序度的变化行为；利用基于密度泛函理论的第一原理计算，研究了不同种类Fe基合金固溶体的晶体结构参数、价电子结构和微观磁性特征，计算和分析了各原子轨道磁矩和态密度变化，探讨了不同成分和温度下合金中电子自旋极化和原子磁矩的演变规律，分析了过渡金属团簇中的自旋有序和自旋/轨道相互作用。.本项目在实验测量和理论计算的基础上，探讨了各因素对Fe基合金微观组织结构与磁结构特征的影响程度及关联关系，构建了“磁有序强化”的定量表征方程。本项目的完成可为磁有序强化方式提供一定的理论基础，对于高温金属材料的设计、开发及工程应用具有重要的理论指导意义。