CHEN Zaisheng, WANG Yanxia
【Objective】 Soft magnetic composites (SMCs) have been widely used in power electronics, motor systems, and high-frequency electromagnetic devices because of their high electrical resistivity, low eddy-current loss, and flexible three-dimensional formability. With the rapid development of new energy equipment and high-frequency electronic systems, higher requirements have been placed on the magnetic performance, thermal stability, dimensional accuracy, and service reliability of SMCs. However, the preparation of high-performance SMCs still faces challenges such as unstable insulation coatings, insufficient densification, difficulty in fabricating complex structures, and limited microstructure control during heat treatment. This review aims to summarize recent progress in SMC preparation technologies and to clarify the influence of major processing routes on microstructure and magnetic properties.
【Method】 This paper reviews the preparation technologies of SMCs from four aspects: insulation coating, forming, sintering, and heat treatment. Physical coating, sol-gel coating, and in situ growth are compared, together with the characteristics of organic, inorganic, and hybrid insulating materials. The effects of cold compaction, warm compaction, and hot pressing on densification and interface bonding are discussed. Conventional sintering and rapid sintering methods, such as spark plasma sintering and microwave sintering, are also analyzed. In addition, the roles of conventional annealing and magnetic-field-assisted heat treatment in stress relief and magnetic-domain regulation are summarized.
【Result】 Existing studies show that insulation coating is a key approach for suppressing eddy-current loss and improving high-frequency performance, but coating type, thickness, and interface adhesion must be carefully controlled to avoid reducing permeability and magnetic flux density. Organic coatings have good processability but poor thermal resistance, whereas inorganic coatings offer better thermal stability but are prone to cracking and interfacial debonding. Hybrid coatings show greater potential, although their interfacial synergy requires further investigation. Improved densification through forming and sintering generally enhances magnetic response and mechanical strength, but excessive pressure or thermal exposure may damage the insulation layer and increase magnetic loss. Heat treatment, especially magnetic-field-assisted annealing, is effective in relieving residual stress, optimizing domain structure, reducing coercivity, and improving the high-frequency magnetic performance of SMCs.
【Conclusion】 Future studies should focus on integrated optimization throughout the full preparation process, including the development of stable insulation systems with strong interfacial bonding, precision forming methods for complex components, efficient sintering routes that preserve insulation integrity, and refined heat-treatment strategies for stress relaxation and microstructure control. More attention should also be paid to the coupling relationship among coating structure, densification, thermal history, and magnetic loss, so as to support the large-scale fabrication and application of high-performance SMCs in high-frequency and high-efficiency devices.
