Study On Preparation Of Fe-Si Magnetic Cores By Mechanical Alloying

Fe-Si alloy is a kind of important functional materials and plays decisive role in energy transformation and information processing. Mechanical alloying(MA) is a newly method to synthesize materials and is expected to produce Fe-Si alloys with high performance.The mechanical alloying process of Fe-Si alloy was investigated.The pressing process, sintering process and magnetic properties of the product were studied in this paper too.Fe-6.5%Si magnetic powders were prepared by two kinds of high energy ball mills, inspectively. Influence of milling condition on milling efficiency was investigated, the optimum condition was found.The optimum technological condition of QM-1SP4 planetary ball mill was as follows: the rotation speed was 365rpm, ball to powder ratio was 10:1, mill mediator was absolute ethyl alcohol, when pill degrees to vent material were 125μm, 60μm and 30μm, the milling time were 9h, 15h and 20h. At the same time, the optimized technique of ZM6A vibratory mill was as follows: ball to powder ratio was 45:1, the content of grinding aid was about 3%. Milling time changed with pill degress to vent material.When pill degress to vent material was 125μm,60μm and 30μm,mill time were 9h (dry milling), 12h(dry milling) and 12h(wet milling) respectively.The results of mechanical alloying experiments showed that the as-milled 12h product was nanostructureα-Fe(Si) solid solution.Complex particles which had bedded structure were formationed when the time was 8h, the concentration of Si atom was gradient distribution.When the time was 12h, the diffusion of Si basicly finished, the concentration of Si atom was homogenous distribution in every particle. What's more, in the research range, there was no amorphous phase formed during the mechanical alloying process of Fe-Si system.Based on the Miedema's semi-empirical theory, the thermodynamic mode for binary system was established to analyze the mechanical alloying of Fe-Si system. In the research composition range, the formation energy of amorphous phase was higher than that of solid solution, so Fe-Si system tended to form solid solution firstly.The content of FeSi75 alloy, milling condition had great influence on green density.The density of compact reduced with the increase of content of FeSi75 alloy, milling time or rational speed. Density of sintered samples rised to large extent than that of not-sintered samples, so the samples became denser.when the content of FeSi75 alloy was 5%, magnetic core had the highest density and the minimum porosity of all magnetic cores.Component had significant effect on magnetic properties of magnetic cores. 5% FeSi75 magnetic core had the best direct current magnetic properties, such as B50 was 1.30T. Core loss lineal increased with the elevation of frequency. Bm of 5% FeSi75 magnetic core was much higher than that of 10% FeSi75 magnetic core at the same frequency. Comparatively, the alternating current magnetic properties of 5% FeSi75 magnetic core were superior to that of 10% FeSi75 magnetic core.