Effects of alloying elements on thermal stability, glass-forming ability and soft magnetic properties of Fe-P-C-B metallic glasses

Fe-based bulk metallic glasses (BMGs) are attractive for the engineering applications as functional materials because of their excellent soft magnetic properties, very high strength, viscous flow workability in the supercooled liquid region (ΔT_x = T_x-T_g, T_g: glass transition temperature; T_g: crystallization temperature), and low material cost [1]. Recently, the thermoplastic processing has been expected to make highly functional micro-/nano-parts and electromechanical devices on the soft magnetic Fe-based BMGs by suing the viscous flow workability [1,2]. The suitable BMGs for thermoplastic processes have to possess simultaneously low T_g, large ΔT_x, and high glass-forming ability (GFA). From a processing point of view, it is desirable to possess a large ΔT_x which gives access to a low forming viscosity, which in turn facilitates thermoplastic forming. A low T_g implies a low processing temperature since it facilitates processing [2]. In addition, a low T_g can prevent the reaction of the metallic glasses with mold materials. However, most of the Fe-based BMGs with good soft magnetic properties exhibited high T_g, small ΔT_x, low GFA or high viscosity in the supercooled liquid state, which hinder their thermoplastic formability. In this work, with the aim of developing new ferromagnetic Fe-based BMGs with low T_g, large ΔT_x and high GFA for the thermoplastic processing, we investigated the effect of alloying additions on the thermal stability, GFA, magnetic properties of the Fe-P-C-B metallic glasses with low T_g.