研究了Tb0.36Dy0.64(Fe0.85Co0.15)1.95合金中替换元素Co的分布及其对材料内禀磁性和本征磁致伸缩性能的影响. EDS分析表明, 合金中产生了Co富集的富稀土相, Co在其中的含量为21.18%(原子分数), 高于基体中Co的含量9.36%. Co元素部分替换Fe未改变巨磁致伸缩合金主相Laves相的结构, 合金的Curie温度从378℃提高到420℃, 拓展了应用温度范围; 同时, Co元素的添加部分补偿了由于Tb/Dy比例提高所增大的磁晶各向异性, 有利于改善合金低场性能. 为避免样品的生长取向对本征磁致伸缩性能测量的影响, 保证测量结果的准确性, 制备了 Tb0.36Dy0.64(Fe0.85Co0.15)1.95无取向等轴晶样品, 测量了合金的饱和磁致伸缩常数 λs. 通过Laves相XRD谱中(440)峰的劈裂, 计算了沿<111>方向上的磁致伸缩λ111, 由此计算出沿<100>方向上的磁致伸缩λ100. 与Tb0.3Dy0.7Fe1.95合金相比, Co添加后λ111稍有降低, λ100得到显著提升, 饱和磁致伸缩常数λs基本相当.
The distribution of Co, the intrinsic magnetism and magnetostriction of quaternary Tb-Dy-Fe-Co alloy were investigated. The SEM image showed the matrix (Laves phase) and the rare-earth (RE) rich phase in the annealed samples. The Co content (atomic fraction) in the RE rich phase was 21.18%, much higher than that in the matrix (9.36%). XRD patterns showed that Co partial substitution for Fe did not change the structure of MgCu2-type cubic Laves phase, contributing to the giant magnetostriction. Curie temperature Tc was increased remarkably with Co addition, resulting in wider operating temperature. The magnetocrystalline anisotropy compensation by Co addition was beneficial to improving the magnetostriction in low field. The solidified orientation influences the testing of intrinsic magnetostriction. In order to ensure the accuracy in the measurements, the equiaxed Tb-Dy-Fe-Co samples were prepared. The saturated magnetostrictive constant λs was tested. λ111 and λ100 were calculated by the cleavage of (440) diffraction peak of Laves phase. Compared with Terfenol-D alloy, λ111 in the Co-doped sample decreased slightly, but λ100 increased evidently and λs almost remained unchanged.
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