Abstract
A supercooled liquid region before crystallization was found in wide composition ranges of 0 to 65 at%Co and 1.5 to 7 at%Ln in Fe 90-x-y Co x Ln y B 20 (Ln=Nd, Sm, Tb or Dy) amorphous alloys. The supercooled liquid region shows the largest value of 41 K for the Fe 47 Co 30 Sm 3 B 20 alloy. Besides, an internal equilibrium state leading to the disappearance of the previous thermal history is achieved within a temperature interval of 15 K. Furthermore, the Fe-Co-Ln-B amorphous alloys exhibit soft ferromagnetism with saturated magnetization (B s ) of 0.84 to 1.66 T and coercivity (H c ) of 5.0 to 36 A/m at room temperature. In addition, a high magnetostriction (λ s ) exceeding 40 × 10 -6 was observed in the composition range of 0 to 10 at%Co and 1.5 to 3 at%Ln (Ln=Sm, Tb or Dy) while the highest λ s reaches 58 × 10 -6 for Fe 68.5 Co 10 Ln 1.5 B 20 (Ln=Sm or Tb), which is higher than the highest value (44 ×10 -6 ) for previously reported amorphous alloys. All the Fe 68.5 Co 10 Ln 1.5 B 20 amorphous alloys have good bending ductility. The tensile fracture strength, Vickers hardness and Young's modulus of the Fe 68.5 Co 10 Sm 1.5 B 20 amorphous alloy are 3220 MPa, 990 and 76.5 GPa, respectively. The good combination of high λ s , high B s , low H c , large ΔT x , good ductility and high mechanical strength is a promising new type of ferromagnetic bulk amorphous alloy.
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