Thermal Stability and Soft Magnetic Properties of Fe-Co-Ga-P-C-B Alloys with High Glass-Forming Ability

Abstract

The effect of ferromagnetic metal Co on the glass-forming ability and magnetic properties for the Fe_75-xCo_xGa₅P₁₂C₄B₄ glassy alloys was investigated. The additions of 10 to 15 at% Co were found to be effective for the extension of the supercooled liquid region (ΔT_x) defined by the difference between the glass transition temperature (T_g) and crystallization temperature (T_x). The ΔT_x value is 37K for the Fe₇₅Ga₅P₁₂C₄B₄ alloy and increases to 48K for the 10, 12.5 and 15at% Co alloys. The liquidus temperature (T₁) of the 10, 12.5 and 15 at% Co alloys decreased by the addition of Co and the reduced glass transition temperature (T_g/T₁) increased. The largest T_g/T₁ is 0.61 for the Fe₆₅Co₁₀Ga₅P₁₂C₄B₄ alloy. These glassy ribbon alloys exhibit good soft magnetic properties of 1.15 to 1.3 T for saturation magnetization and 2.4 to 3.3 A/m for coercive force. Based on the large ΔT_x and high T_g/T₁ values, we tried to prepare bulk glassy Fe_75-xCo_xGa₅P₁₂C₄B₄ (x=10, 12.5, 15) rods in a cylindrical form with different diameters. The glassy single phase was obtained in the diameter of 1.5mm in the composition range of 10 to 15 at% Co. Furthermore, for the Fe₆₅Co₁₀Ga₅P₁₂C₄B₄ alloy, a bulk glassy rod with good soft magnetic properties in diameter of 2mm was formed.