Mechanical and magnetostrictive properties of Tb_0.36Dy_0.64 (Fe_1-xMn_x)_1.9 alloys

The magnetization, magnetostriction and compressive strengths of arc-cast polycrystalline and directionally solidified Tb_0.36Dy_0.64 (Fe_1-xMn_x)_1.9 (x=0, 0.05, 0.10, 0.15, 0.20) rods were investigated by VSM, standard strain gauge method and compressive tests, respectively. The results show that the magnetostriction λ_s, saturation magnetization M_s and magnetocrystalline anisotropy constant K₁ decrease with increasing the Mn concentration. The optical micrographs and XRD patterns show that the Tb_0.36Dy_0.64 (Fe_1-xMn_x)_1.9 alloys are composed of MgCu₂-type Laves phase as matrix and a small amount of rare-earth rich phase. It is found that the distribution of the rare-earth rich phase has an important effect on mechanical property of Tb_0.36Dy_0.64 (Fe_1-xMn_x)_1.9 samples. For the arc-cast samples, smaller equal-axial grains are arranged irregularly, which results in higher compressive strengths. However, the rare-earth rich phase is arranged as parallel arrays in the directionally solidified samples, which leads to smaller compressive strengths.