Influences of surface state on thermal stability and magnetic properties of Fe-Si-B-C amorphous alloy

Influences of surface state on thermal stability and magnetic properties for Fe82Si1B12C5 completely amorphous alloys and Fe83Si1B12C4 amorphous alloys with partial crystallization at their surface have been investigated by layer polished-removal method. The crystallization enthalpy of alpha-Fe phase for the two amorphous alloys decreases obviously with polishing removal of surface layer with the thickness of removal, due to the alteration of internal stress state. An increase of only 1.2% in Fe content causes an increase of 8.4% in crystallization enthalpy of alpha-Fe phase for the alloy system with an initial casting thickness, indicating that the thermal stability is stress-sensitive for Fe-based amorphous alloys with high Fe content close to amorphous forming boundary are easier to crystallize. It was found that in the as-quenched state the coercivity for both of them increases linearly with the thickness of removal, which is caused by an increase in internal stress. And it was confirmed by experiment that adequate annealing can greatly improve the soft magnetic properties and alter thermal stability.