Effects of crystallization on the coercivity in Fe78Si9B13 amorphous alloy

Attempts were made to correlate the coercivity with microstructural evolution in order to understand the origin of magnetic hardening of an Fe78Si9B13 amorphous alloy. This metallic glass was devitrified so as to produce a series of specimens with increasing crystallinity. Initially, the coercivity increases with increasing density of α-iron crystallites in the glassy matrix. The maximum coercivity is obtained after a heat treatment at 600 °C for 30 min. The microstructure of the alloy with maximum coercivity is characterized by α-iron grains which coexist with a metastable lamellar Fe3B compound at the grain boundaries. For high temperature anneals the replacement of the Fe3B phase by equilibrium Fe2B with equiaxed morphology caused the coercivity to decrease.