Thermal Stability and Crystallization οf Iron and Cobalt - Based Bulk Amorphous Alloys

Microstructure by the Mössbauer spectroscopy and approach to magnetic saturation in the bulk amorphous Fe 61 Co 10 Me 7 Y 2 B 20 (Me 7 = Y 7 , Y 6 Ti 1 or Zr 2.5 Hf 2.5 W 2 ) alloys are investigated.The bulk amorphous Fe61Co10Zr2.5Hf2.5W2Y2B20alloy exhibits the best thermal stability and remains amorphous up to 901 K.Moreover, the quasi-dislocations dipoles present in this amorphous alloy have the largest width equal to 6.7 nm.After annealing this alloy below the crystallization temperature the enhancement of both the average hyperfine field and its standard deviation is observed which points to the increase in the atom packing density due to the decay of quasi-dislocation dipoles.After the annealing at 901 K the small amount of the crystalline α-FeCo phase is presented in this alloy.The same crystalline phase appears in the bulk Fe61Co10Y8Ti1B20 and Fe61Co10Y9B20 alloys after annealing at 750 K and 840 K, respectively.