微量稀土元素Tb、La掺杂对Fe-Al合金结构和磁致伸缩性能的影响

为了研究微量稀土元素Tb和La掺杂对Fe81Al19合金结构和磁致伸缩性能的影响及影响机制,采用真空电弧熔炼法制备了Fe81Al19、Fe81Al19La0.1和Fe81Al19Tb0.1三种铸态合金。用X射线衍射仪(XRD)和扫描电镜联合能谱仪(SEM/EDS)分析了合金的微结构。用振动样品磁强计(VSM)和磁致伸缩测量仪测试了合金的磁性能和磁致伸缩系数。结果表明,Fe81Al19合金由单一的bcc结构A2相组成,而掺杂稀土后的Fe81Al19Tb0.1和Fe81Al19La0.1合金均由bcc结构的A2主相和少量富稀土相组成。稀土Tb和La的掺杂使Fe81Al19合金沿<100>晶向择优取向,且Fe81Al19Tb0.1合金择优取向更加明显。此外,三种合金的磁化功大小排序为:Fe81Al19Tb0.1> Fe81Al19La0.1> Fe81Al19。表明稀土元素掺杂导致Fe-Al合金具有更大的磁晶各向异性,且Tb的掺杂效果更加明显。磁致伸缩系数测试表明,与Fe81Al19合金相比,稀土掺杂合金的磁致伸缩系数明显增大,而且Fe81Al19Tb0.1合金的磁致伸缩系数增大的更加明显,大约是Fe81Al19合金的3.2倍,为86×10^-6。稀土掺杂合金磁致伸缩系数增大的原因主要源于掺杂稀土使Fe-Al合金沿<100>晶向择优取向和稀土导致合金具有高磁晶各向异性。

Effects of Tb and La Doping on Microstructure and Magnetostriction of Fe-Al Alloys

In order to study the effect and mechanism of trace rare earth elements Tb and La doping on the structure and magnetostrictive properties of Fe81Al19 alloy, the polycrystalline Fe81Al19, Fe81Al19La0.1 and Fe81Al19Tb0.1 as-cast alloys were prepared by vacuum arc melting. The microstructure of the alloy was analyzed by X-ray diffraction(XRD), scanning electron microscope and energy dispersive spectroscopy(SEM/EDS). The magnetic properties of the alloy were tested by vibration sample magnetometer(VSM). The magnetostrictive properties of the alloys were measured by a strain gauge method. The results showed that the Fe81Al19 alloy consists of a single A2 phase with bcc structure, while Fe81Al19Tb0.1 and Fe81Al19La0.1 alloys consist of the A2 main phase and a small amount of rare earth-rich phases. The doping of the rare earth elements La and Tb makes the A2 phase of Fe81Al19 alloy preferentially oriented in the <100> crystal direction. The preferred orientation of Fe81Al19Tb0.1 alloy is more obvious than that of Fe81Al19La0.1 alloy. In addition, the sequence of the magnetization work of the three alloys is: Fe81Al19Tb0.1>Fe81Al19La0.1>Fe81Al19. Therefore, we can infer that the doping of rare earth element causes greater magnetocrystalline anisotropy of the Fe-Al alloy, and rare earth element Tb causes more obvious effects. The magnetostrictive coefficient test showed that, compared with Fe81Al19 alloy, the magnetostrictive coefficient of the Fe81Al19 alloy doped with rare earth increases significantly, and the magnetostrictive coefficient of Fe81Al19Tb0.1 alloy increases the most, its magnetostriction coefficient is about 3.2 times that of Fe81Al19 alloy, which is 86×10^-6. The increase of the magnetostrictive coefficient of Fe81Al19 alloys doped with rare earth is mainly attributed to the preferred orientation along the <100> crystal orientation of A2 phase of the alloy and the high magnetocrystalline anisotropy of the alloy caused by the rare earth.