【作者】 张智；

【导师】 杨超； 柯海波；

【作者基本信息】 华南理工大学 ， 材料与化工（专业学位）， 2023， 硕士

【摘要】 在环境保护与节约能源的大背景下,软磁材料正不断朝着小型化、节能化、高效化以及高频化的方向发展。而铁基非晶/纳米晶合金作为软磁材料里的一种新型材料,具有比其他软磁材料更优异的软磁性能,如高饱和磁感、高电阻率等,广泛应用于变压器、感应器、滤波器、隔离器等设备。尽管铁基非晶磁粉芯在高功率、高频率、高温度等方面有着明显的优势,但是,它们的生产工艺相对较为复杂,且制造工艺难度大,故其应用被大打折扣。此外,铁基非晶仍有许多制备工艺难以克服,如条带制备、粉末制备、压制成型、低温烧结等,且目前还处于研究阶段。为此,本论文研制了高P含量的FeSiBPCuC非晶合金材料,探索了淬态非晶相的组织结构和软磁性能,并对其晶化激活能进行了计算,着重分析了不同退火温度和保温时间对条带组织结构和软磁性能的影响规律。同时,通过对高P含量FeSiBPCuC合金不同升温速率下的晶化行为进行研究,建立了快慢速升温下的晶化模型,为其大规模工业化生产提供理论指导。最后,通过条带破碎法制备完全非晶合金,研究了不同工艺参数对软磁性能的影响,获得了具有优异综合软磁性能的磁粉芯。首先,使用单辊快淬技术制备了四种高P含量的FeSiBPCuC非晶合金条带,P元素含量为8.93～11.65 at.%,根据P含量带来Fe含量的变化,并对其淬态组织结构和软磁性能进行研究。结果发现:当Fe含量小于83.5 at.%时,淬态非晶基体中无初晶相,随着Fe含量提高,高P含量的淬态FeSiBPCuC合金的M_s逐渐提高,H_c逐渐降低。此外,通过晶化激活能计算发现,当Fe含量为82.5 at.%时具有最高的激活能(E_x1=270.5 k J/mol),说明Fe82.5具有较好的非晶形成能力和热稳定性。进而,通过对不同退火温度下组织结构和软磁性能的表征,发现Fe82.5在360～410℃范围内具有优异的综合软磁性能,说明Fe82.5具有较好的工艺稳定性以及较宽的热处理温度窗口。再者,通过对不同保温时间的研究发现,Fe82.5和Fe83.5在保温至等温曲线顶点处有最佳的软磁性能,揭示了退火温度和保温时间之间的关系,同时,也为制定热处理工艺提供了重要的参考依据。随后,基于等温晶化行为分析,系统研究了不同升温速率下的等温晶化规律。结果表明,等温阶段孕育时间随着升温速率的提高而延长,在一定升温速率下,孕育时间趋近于一个固定值,等温晶化峰趋于一致。对于高P含量的FeSiBPCuC合金而言,当升温速率达到一定值时,升温过程对非晶基体的影响是一致的。基于此,本文阐明了快慢速升温对晶化行为和软磁性能的影响规律,并建立了快慢速升温下的晶化模型。慢速升温有利于淬态下无初晶相的高P含量FeSiBPCuC合金条带获得更加优异的软磁性能。在慢速升温过程中,在非晶基体中析出大量均匀分布的Cu团簇和细小初晶相,为等温过程的共同竞争晶化机制创造了有利的条件。而快速升温至等温阶段,淬态不发生改变,等温过程Cu发生团簇和α-Fe晶粒的同时析出,使得α-Fe晶粒发生团聚长大现象,从而恶化了磁性能。因此,可通过调控升温速率使得非晶基体中形成均匀分布的Cu团簇和初晶相,为等温晶化过程提供大量的形核位点,获得细小且均匀分布的α-Fe晶粒,从而获得优异的综合软磁性能。通过上述研究,得到高饱和磁化强度的Fe82.5合金作为核壳功能基元的核结构,绝缘层作为壳结构。利用条带破碎法制备高P含量FeSiBPCuC合金粉末,对核壳功能基元进行调控,并研究不同核壳结构对软磁性能的影响规律。得到高电阻率（3394.49μ?·cm）、高饱和磁化强度（188.7 emu/g）、高磁导率（99.1）、低损耗（295.9 m W/cm³（B_m=50 m T;?=100 k Hz））以及具有良好频率稳定性（10 MHz）的非晶磁粉芯。更多还原

【Abstract】 With the context of environmental protection and energy saving,soft magnetic materials are developing towards miniaturization,energy saving,high efficiency and high frequency.As a new type of soft magnetic materials,Fe-based amorphous/nanocrystalline alloy has better soft magnetic properties than those of other soft magnetic materials,such as high saturation magnetic inductance,high resistance,etc.It is widely used in transformers,inductors,filters,insulators and other devices.Although Fe-based amorphous powder cores have obvious advantages in terms of high power,high frequency and high temperature,their production process is relatively complex and the manufacturing process is difficult,resulting in their limited applications.In addition,there are still many processing problems for Fe-based amorphous alloy,such as strip preparation,powder preparation,compaction forming,and low-temperature sintering,which are difficult to be overcome and are still in the research stage.In this work,high P content FeSiBPCuC amorphous alloys were studied and prepared,and their microstructure and soft magnetic properties of quenched amorphous phases were investigated.Corresponding crystallization activation energy was also calculated,and the influence of different annealing temperatures and holding times on the microstructure and soft magnetic properties was emphasized.At the same time,the crystallization behavior of the high P content FeSiBPCuC alloys under different heating rates was studied,and thus the crystallization models under fast and slow heating rates were established to provide theoretical guidance for their ability to be industrially produced on a large scale.Finally,the effect of different process parameters on the soft magnetic properties was investigated by using the strip crushing method to prepare a completely amorphous alloy and thus obtain a magnetic powder core with excellent integrated soft magnetic properties.First,four FeSiBPCuC amorphous alloy ribbons with high P content were prepared by using the single-roller fast quenching technique,The elemental P content ranged from 8.93 to11.65 at.%,according to the variation of Fe content brought by P content,and their quenched microstructures and soft magnetic properties were investigated.It was found that there was no primary crystalline phase in the quenched amorphous matrix when the Fe content was less than83.5 at.%,and corresponding M_s of the quenched FeSiBPCuC alloys gradually increased and the H_c gradually decreased as the Fe content increased.In addition,the crystallization activation energy revealed that the highest activation energy(E_x1=270.5 k J/mol)was found when the Fe content was 82.5 at.%,indicating that Fe82.5 amorphous alloy has better amorphous formation ability and thermal stability.Further,by characterizing the microstructure and soft magnetic properties at different annealing temperatures,it was found that Fe82.5 amorphous alloy has excellent comprehensive soft magnetic properties in the range of 360-410°C,indicating that Fe82.5 has better process stability as well as a wide heat treatment temperature window.Furthermore,the study of different holding times revealed that Fe82.5 and Fe83.5 had the best soft magnetic properties at the top of the isothermal curve,revealing the relationship between annealing temperature and holding time,and also providing an important reference for the development of the heat treatment process.Subsequently,the isothermal crystallization behavior was systematically studied based on isothermal curves at different heating rates.The results show that the incubation time of the isothermal stage increases with the increase of different heating rates.At a certain heating rate,the incubation time tends to a fixed value and the isothermal crystallization peaks tend to be consistent.For the FeSiBPCuC alloy with high P content,the effect of the heating process on the amorphous matrix is consistent when the heating rate reaches a certain value.Based on this,the effect of fast and slow heating rates on the crystallization behavior and soft magnetic properties is elucidated in this paper,and corresponding crystallization model is established.A series of studies show that the slow heating rate is beneficial for the high P content FeSiBPCuC alloy ribbons without primary crystalline phase in the quenched state to obtain more excellent soft magnetic properties.Basically,a large number of uniformly distributed Cu clusters and fine primary crystalline phases are precipitated in the amorphous matrix,creating favorable conditions for the co-competitive crystallization mechanism in the isothermal process.While the rapid heating rate to isothermal stage,the quenching state does not change,and the isotherma Cu clusters andα-Fe grains precipitation occurs simultaneously,which makes theα-Fe grains agglomerate and grow,thus deteriorating the magnetic properties.Therefore,the temperature heating rate can be controlled to form uniformly distributed Cu clusters and primary crystalline phases in the amorphous matrix,providing a large number of nucleation sites for the isothermal crystallization process and obtaining small and uniformly distributedα-Fe grains,thus achieving excellent overall soft magnetic properties.Finally,the Fe82.5 alloy with high saturation magnetization was made into the core structure of the core-shell functional unit,and the insulating layer was used as the shell structure.The high P content FeSiBPCuC alloy powder was prepared by ribbon crushing method to modulate the core-shell functional units and to investigate the influence of different core-shell structures on the soft magnetic properties.Amorphous magnetic powder cores with high resistivity（3394.49μΩ·cm）,high saturation magnetization（188.7 emu/g）,high permeability（99.1）,low loss（295.9 m W/cm³（B_m=50 m T;?=100 k Hz））and good frequency stability（10MHz）were obtained.更多还原