Influence of Microstructure on Microhardness of Fe81Si4B13C2 Amorphous Alloy after Thermal Treatment

The influence of microstructure, and its changes, on microhardness of the amorphous Fe81Si4B13C2 alloy after thermal treatment at different temperatures from 298 K to 973 K (25 A degrees C to 700 A degrees C) was studied. The as-prepared alloy ribbon containing a small amount of crystalline phases, as well as domains of short-range crystalline ordering embedded in the amorphous matrix, exhibits unexpectedly high microhardness, mostly due to its composition. After thermal treatment above 723 K (450 A degrees C), the alloy samples begin to crystallize, creating a nanocomposite structure involving nanocrystals embedded in an amorphous matrix, leading to an increase in microhardness. Further growth of the nanocrystals, as the heating temperature was increased to 973 K (700 A degrees C), caused the change from nanocomposite structure into a more granulated and porous structure, with a dominant type of interface changing from amorphous/crystal to crystal/crystal, leading to a decrease in microhardness.