超稳铁基金属玻璃能量状态对软磁性能的影响及其物理机制研究

The nonequilibrium fast-cooling process for fabricating metallic glasses causes strong internal stress and structural heterogeneity. As a result of magneto-elastic coupling interaction, the soft magnetic properties of Fe-based metallic glasses get deteriorated. The ultrastable Fe-based metallic glasses, which have high stability and very low energy, probably have weak internal stress and exhibit excellent soft magnetic properties. In this proposal, we will fabricate ultrastable Fe-based metallic glasses with low energy by controlling the relaxation temperature and relaxation time. The optimal parameters for fabricating ultrastable Fe-based metallic glasses will be determined. The quantitative relationship between soft magnetic parameters and energy of Fe-based metallic glasses will be studied. By measuring the relaxation kinetics and the evolution of relaxation activation energy, different relaxation modes will be distinguished and their influence on soft magnetic properties will be studied. By studying the evolutions of micro heterogeneity of mechanical properties and magnetic domains along with the relaxation, their correlation will be established to explain the micro mechanism for the influence of energy states on soft magnetic properties of ultrastable Fe-based metallic glasses. These results are expected to be helpful for designing new metallic glasses with excellent soft magnetic properties.

急冷方法制备金属玻璃属于非平衡凝固过程，将会引起严重的内应力和结构不均匀性，对软磁性能不利。超稳铁基金属玻璃具有高稳定性、极低的能量状态和均匀的结构，有可能具有非常低的内应力，从而表现出非常优异的软磁性能。本项目拟通过调节弛豫温度和时间，制备具有低能量状态的高稳定性铁基金属玻璃，研究制备超稳铁基金属玻璃的最优化条件以及金属玻璃能量状态与软磁性能之间的定量关系；通过测量弛豫动力学随着退火温度和时间的演化，计算弛豫激活能，研究不同弛豫模式对软磁性能的影响；通过研究微观结构不均匀性和磁畴随着弛豫过程的演化规律，解释铁基金属玻璃软磁性能随着能量状态变化的微观机制。这些结果将为研发具有优异软磁性能的金属玻璃提供新思路。

本工作以低能量超稳非晶合金的制备为切入点，研究弛豫和晶化规律，并系统研究超稳特性对铁基非晶合金软磁功能特性的影响规律和机制。在本项目主要成果如下：（1）发现单一温度等温退火过程并不是单一的弛豫动力学过程，而是先后经历了β弛豫和α弛豫。（2）β弛豫能够有效改善Fe基非晶合金软磁性能，同时保持良好的力学性能；α弛豫阶段对软磁性能没有明显影响，但力学变形能力变差，非晶合金变脆。（3）深入研究β弛豫影响磁性能的微观机理，发现β弛豫对应的不均匀性结构与磁畴壁之间存在耦合作用，符合磁弹耦合理论，磁畴壁厚度约36nm，与结构涨落尺度相当，存在耦合。（4）研究了双步等温退火过程中，反常弛豫——记忆效应产生的物理起源，即超低能量深度弛豫伴随的大激活熵是触发记忆效应的关键。这些研究结果不但可以深刻认识非晶合金中的磁弹耦合相互作用及其微观物理机制，亦可以为研发具有更加优异软磁性能的新型非晶合金、改善铁基非晶合金生产工艺提供理论指导。