Effect of cu addition on nanocrystallization behaviors and magnetic properties of the Fe_76.5-xC_6.0Si_3.3B _5.5P_8.7Cu_x (x = 0-3 at.%) bulk metallic glass

The effect of Cu addition on the glass forming ability, nanocrystallization process and soft magnetic properties of the Fe_76.5C _6.0Si_3.3B_5.5P_8.7 bulk metallic glass has been studied. In spite of relatively high C contents of the alloy, with only 0.5% Cu addition, the primary phase was successfully changed from metastable carbide Fe₂₃C₆ phase to stable alpha-Fe phase and the nucleation rate at the early stage of crystallization was significantly increased. Nanocrystallization of the Fe_76.0C_6.0Si _3.3B_5.5P_8.7Cu_0.5 (at.%) bulk metallic glass was studied through isothermal annealing treatments at temperature below the crystallization temperature of the alloy. With annealing at T_x - 50 °C for 30 min, a large number of very fine regions (<3 nm) with ordered atomic arrangements embedded in the amorphous matrix were observed. Upon further annealing, nanocrystals of alpha-Fe phase were formed improving soft magnetic properties of the sample, which confirms the soft magnetic nanocrystallization phenomenon in Fe_76.0C _6.0Si_3.3B_5.5P_8.7Cu_0.5 (at.%) bulk metallic glass. By controlling the annealing parameters as well as minor Cu contents, magnetic properties of the Fe_76.5C _6.0Si_3.3B_5.5P_8.7 (at.%) bulk metallic glass were effectively optimized for practical applications.