Thermal stability and magnetic properties of Fe-Al-Ga-P-C-B-Si amorphous thick sheets

The structure and magnetic properties of melt-spun multicomponent Fe₇₂Ga₂Al₅P_11-xC₆ B₄Si_x (x=0-10) alloy sheets were investigated. The increases in the thermal stability and glass forming ability, and the improvement of the soft magnetic properties were recognized with the replacement of P by 1-2 at% Si. The supercooled liquid region (ΔT_x) defined by the difference between crystallization temperature (T_x) and glass transition temperature (T_g) increases from 51 K for the Fe₇₂Al₅Ga₂P₁₁C₆B ₄ alloy to 65 K for the Fe₇₂Al₅Ga₂ P₉C₆B₄Si₂ alloy, and then decreases with increasing Si content. The maximum thickness for glass formation (t_max) also increases from 140 μm for the Fe₇₂Al₅Ga₂P₁₁C₆B ₄ alloy to 190 μm for the Fe₇₂Al₅Ga ₂P₉C₆B₄Si₂ alloy. The increases in ΔT_x and t_max are presumably because of increased agreement with three empirical rules for glass formation. The soft magnetic properties at the thickness of over 70 μm are also improved by the replacement of 1-2 at% Si. The magnetic properties for the Fe₇₂Al₅Ga₂P₉ C₆B₄Si₂ amorphous alloy with the thickness of 190 μm after optimum annealing (623 K×1.8 ks) are 169×10^-6 Wbmkg^-1 for saturation magnetization (σ_s), 1.0 A/m for coercive force (H_c ), and 9000 for permeability (μ_e) at 1 kHz. It is therefore expected that the Fe-based amorphous alloy containing 2 at% Si is widely used as a bulk amorphous material with good soft magnetic properties