Production of Fe-35.2Co-4.3B-2.8Si-7.7Nb (wt.%) Bulk Metallic Glass alloy Strips by Spray Rolling Process

Spray rolling of the Fe-35.2Co-4.3B-2.8Si-7.7Nb (wt.%) bulk metallic glass (BMG) alloy was performed with the aim of obtaining a fully amorphous structure. To estimate the cooling rate imposed on the alloy during the process, aluminum Al-8.8Si-1.3Cu (wt.%) alloy (ASTM A380) samples were produced by the same process. The secondary dendritic arm spacing (λ2) obtained in the aluminum strips was used to calculate the cooling rate, applying Equations based on the classical correlation between secondary dendritic arm spacing (λ2) and the local solidification time (tsl). Both alloys were atomized onto copper rolls rotating at 4.46 m/s generating thin strips with 150 mm mean width and several centimeters long. The cooling rate of the spray rolling process was evaluated as approximately 105 K/s, enabling to obtain fully amorphous thin strips of the bulk metallic glass alloy.