Development of Biocompatible Fe-Pt Based Magnetic Materials

从前人对铁铂基永磁体的研究结果可以看出，这种磁体合金具有耐腐蚀性、可铸性、磁性能和表面粗糙度等优点，非常适合作为假体应用。为了将该合金应用于临床，必须开发出具有良好生物相容性和磁性的结构。然后，在本项目中，我们研究了由Fe-PT合金组成的永磁体和保持器的磁体结构，从磁性能、耐腐蚀性和铸造性方面进行了研究。此外，还研究了由耐蚀不锈钢组成的护栏结构。低铂含量的Fe-铂合金在高导热系数的铸型和固溶处理后，表现出优异的软磁和电化学性能，作为保持器材料。为了获得最佳的铁铂基永磁体与富铂铁铂合金保持器之间的最大吸力，对其进行了磁场分析，得到了由沿厚度方向磁化的圆形永磁体四极和直径大于永磁体直径的保持器组成的优化结构。结果表明，富铂铁铂合金护栏的磁体结构比不锈钢护栏具有更高的耐腐蚀性。对微量元素添加效果的研究表明，轻元素的添加促进了组织的细化，改善了加工性能和力学性能。总结本项目的研究成果，认为永磁体和保持器均由具有优良电化学性能的Fe-铂合金组成的磁体结构具有较高的生物相容性和临床应用的可能性。

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.