Abstract: Magnesium aluminum silicate gel was employed as a coating agent for gas-atomized spherical FeSiAl alloy magnetic powder in this work. The coated magnetic powders were pre-heated to explore the effects of preheating process parameters on the surface microstructure of FeSiAl magnetic powder and the performance of the prepared composite magnetic powder cores. The results showed that magnesium aluminum silicate could uniformly coat on the surface of FeSiAl magnetic powder particles. After preheating the coated magnetic powder, the interlayer hydroxyl groups (-OH) in the magnesium aluminum silicate coating were removed.The proportion of Fe0 and Fe2+ on the magnetic powder surface decreased, while elemental Al and Si were oxidized, accompanied by an increase in the content of Al3+ and Si4+. During preheating treatment, recrystallization occurred within the magnetic powder, resulting in an increase in grain size. The elimination of lattice distortion reduced the unit cell parameters, which significantly decreased the coercivity (Hc) of the magnetic powder. Meanwhile, the release of internal stress increased the saturation magnetization. In addition, slight agglomeration of magnetic powder particles appeared after preheating treatment, which reduced the density (ρ) and substantially lowered the effective permeability (μe) of the prepared composite magnetic powder cores. The eddy current loss (Pe) of the magnetic powder was almost unaffected before and after the preheating treatment of magnetic powder, while the hysteresis loss (Ph) was greatly reduced, resulting in a remarkable decrease in core loss (Pcv). When the magnesium aluminum silicate coating content was 1.0wt%, compared with the un-preheated coated magnetic powder, the μe of the composite magnetic powder decreased from 86.0 to 50.2. Under the conditions of 100 mT magnetic induction intensity and 50 kHz frequency, the Pcv decreased from 181.5 kW/m3 to 103.0 kW/m3. With the consistent preparation conditions of composite magnetic powder cores, the μe decreased with the increase of magnesium aluminum silicate coating content, whereas Pcv remained nearly unchanged across all samples.

Key words: FeSiAl magnetic powder, heat treatment, magnesium aluminum silicate, effective permeability, power loss

摘要： 本工作以层状硅酸镁铝凝胶为气雾化球形FeSiAl合金磁粉的包覆剂，并对包覆改性后的磁粉进行预热处理，系统研究预热处理工艺对FeSiAl磁粉表面微观结构及复合磁粉芯性能的影响。结果表明，硅酸镁铝在FeSiAl磁粉颗粒表面均匀包覆；包覆磁粉在热处理后，包覆层内硅酸镁铝层间羟基(-OH)脱除，磁粉表面Fe0和Fe2+所占比例下降，同时单质Al和Si发生氧化，Al3+和Si4+含量增加。预热处理过程中，磁粉内发生再结晶导致晶粒尺寸增大，晶格畸变消除使晶胞参数减小，矫顽力(Hc)显著降低，内应力的释放使饱和磁化强度增大。此外，预热处理后，磁粉颗粒存在少量团聚现象，制备的复合磁粉芯密度(ρ)下降，有效磁导率(μe)显著降低。磁粉预热处理前后，复合磁粉芯涡流损耗(Pe)无明显变化，但磁滞损耗(Ph)大幅下降，导致功率损耗(Pcv)明显减小。当硅酸镁铝包覆量为1.0wt%时，相较于未预热处理的包覆磁粉，复合磁粉芯μe由86.0降低至50.2；在磁感应强度100 mT、频率50 kHz下，Pcv从181.5 kW/m3降至103.0 kW/m3。在复合磁粉芯相同制备条件下，随硅酸镁铝包覆量增加，复合磁粉芯μe下降，但Pcv无明显变化。

关键词: FeSiAl磁粉, 热处理, 硅酸镁铝, 有效磁导率, 功率损耗