Development of Biocompatible Fe-Pt Based Magnetic Materials

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From previous research results of Fe-Pt based permanent magnets, this magnet alloy was found to have the advantages of corrosion resistance, castability, magnetic properties and surface roughness, and so, desirable to applications as prosthesis. In order to apply this alloy clinically, structures with excellent biocompatibility and magnetic properties should be developed. Then, in this project, we investigated magnet structures in which permanent magnet and keeper consist of Fe-Pt alloys, with respect to magnetic properties, corrosion resistance and castability. Structures in which keeper consists of corrosion resistive stainless steel were also investigated. Fe-Pt alloys with low Pt compositions, cast in a mold with high heat conductivity and solution treated, show excellent soft magnetic and electrochemical properties as keeper materials. In order to obtain the optimized maximum attractive force between the Fe-Pt based permanent magnet and Pt-rich Fe-Pt alloy keeper, magnetic field analysis was performed, resulted in the optimized structure consisted of a circular-shaped permanent magnet quadrapole magnetized in the direction along the thickness and a keeper with a diameter larger than that of a permanent magnet. The magnet structure with Pt-rich Fe-Pt alloy keeper is found to have higher corrosion resistivity than the case of stainless keeper. Investigation of minor element addition effect shows that light element addition promotes finer crystal grain structures and improves workability and mechanical properties. Summarized research results in this project is that the magnet structure in which both permanent magnet and keeper consist of Fe-Pt alloys with excellent electrochemical properties is suggested to have high biocompatibility and the possibility of clinical application.