Effect of Tb addition on the thermal stability, glass-forming ability and magnetic properties of Fe-B-Si-Nb bulk metallic glass

摘要

The thermal stability, crystallization behavior, glass-forming ability (GFA), as well as magnetic and mechanical properties of (Fe_(0.75-x)Tb_xB_(0.2)Si_(0.05))_(96)Nb_4 {x = 0.01-0.07) bulk metallic glasses (BMGs) with Tb addition were investigated. With the increase of Tb content, the glass transition temperature (T_g) and the crystallization temperature (T_x) shifted towards higher temperature. The supercooled liquid region (ΔT_x = T_x - T_g) increased from 46 to 100 K for alloy with x = 0.04, due to the tendency to form Fe_(23)B_6 phase and local chemical short-range ordering. Besides, the x = 0.04 alloy decreased the liquidus temperature (T_1) and approached alloy to a eutectic point, leading to the best GFA with a diameter of 3.5 mm. The BMGs exhibited high compressive fracture strength of 3300-4000 MPa and high Vickers hardness of 1020-1110, combined with good soft-magnetic properties, i.e., high saturation magnetic flux density of 0.52-1.14 T, coercive force as low as 2.5 A/m. The mechanisms for high GFA and characteristic exothermic event in the supercooled liquid for the (Fe_(0.75_x)Tb_xB_(0.2)Si_(0.05))_(96)Nb_4 BMGs were discussed.