MnZn-FeNi复合烧结软磁材料的烧结过程和性能研究

Sintering Processes and Properties of MnZn-FeNi Composite Sintered Soft Magnets

采用粉末冶金法制备了MnZn-FeNi复合软磁材料,采用排水法、金相显微镜和X射线衍射仪等手段,研究了样品的烧结过程、坯体的致密化、晶粒生长规律、样品的相结构。采用物理性能综合测试仪(PPMS)测定烧结体的磁性能,研究了材料的微观结构和材料软磁性能之间的关系,分析了样品磁性能变化规律。研究表明,样品密度随烧结温度升高而增大,当烧结温度超过1673K以后,密度变化趋缓。在烧结过程中,影响材料致密性的主要因素为材料中的气孔和晶粒。随烧结温度升高,气孔向晶界和样品表面迁移,并且合并长大,同时,晶粒也发生长大。复合烧结软磁中的FeNi合金和MnZn软磁铁氧体仍保持原有的相结构,在1773K的较高烧结温度时,软磁铁氧体出现分解,产生了部分杂相。通过优化烧结工艺,复合烧结软磁材料的烧结温度在1573～1673K范围内时,样品取得了较好的磁性能,其磁性能为初始磁导率μi=1128,饱和磁化强度Ms=4349kA·m-1。

MnZn-FeNi composite soft magnetic materials were prepared by powder metallurgy technique.Sintering processes of samples,densifying processes of roughcasts,law of grain growth,and phase structure of samples were systematically investigated by dewaterinig method,metallographic microscope and X-ray diffractometer,etc.Magnetic properties of sintering samples were measured with physical property integration measurement system（PPMS）.The relation between microstructure and soft magnetic properties were studied,and the variation of magnetic properties was analyzed.The results showed that the density of the samples increased with the sintering temperature rising.The increase of density slowed down,when the sintering temperature was above 1673 K.In the process of sintering,the change of void and grain in the samples had primary effect on the compactness.With sintering temperature going up,the void moved to grain boundary and surface of the samples,partly amalgamated and grew up,at the same time,the grain also grew up.FeNi alloys and MnZn ferrite in the composite soft magnetic materials remained original phase components,but at the higher sintering temperature of 1773 K,the ferrite began to decomposed,and a small quantity of impurity occurred.The appropriate sintering temperature ranged from 1573 K to 1673 K,the optimal magnetic properties were obtained,initial permeability μi=1128,saturation magnetization Ms=4349 kA·m-1.