Processing soft ferromagnetic metallic glasses: on novel cooling strategies in gas atomization, hydrogen enhancement, and consolidation

Processing soft ferromagnetic glass-forming alloys through gas atomization and consolidation is the most effective technique to produce bulk samples. The commercial viability of these materials depends on commercial purity feedstock. However, crystallization in commercial purity feedstock is several orders of magnitude faster than in high purity materials. The production of amorphous powders with commercial purity requires high cooling rates, which can only be achieved by extending the common process window in conventional gas atomization. The development of novel cooling strategies during molten metal gas atomization on two model alloys ({(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 and Fe76B10Si9P5) is reported. Hydrogen inducement during liquid quenching significantly improved the glass-forming ability and soft magnetic properties of {(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 powders. Spark plasma sintering experiments verified that amorphous rings could be produced regardless of the cooling strategies used. While the saturation magnetization was almost unaffected by consolidation, the coercivity increased slightly and permeability decreased significantly. The magnetic properties of the final bulk samples were independent of feedstock quality. The developed cooling strategies provide a great opportunity for the commercialization of soft ferromagnetic glass-forming alloys with commercial purity.