Effect of compositional elements and processing routes on structural and thermal response in Fe-based metallic glasses

The effect of varying thickness on structure and thermal properties is investigated in Fe-B-Nb and Fe-B-Si-Nb glassy alloy systems with the addition of different Nb and Co content, respectively. Accordingly,four alloys with the nominal compositions of Fe76-xB18Nb6+x (x = 0, 2) and (Fe1-yCoy)72B12Si12Nb4 (y = 0,0.5) are processed in the forms of ribbon and rod. All alloys of ribbons represent amorphous structure,while those of rods explain the crystalline structure with the exception of heteromorphous structure for
Co added alloy. The Nb addition causes about same glass transition temperature (Tg) but increases crystallization onset (Tx), resulting in a wider supercooled liquid region (deltaTx =Tx-Tg). Moreover, Nb also improves glass forming ability (GFA) with more free volume generation and higher structural relaxation exothermic heat (delta H0). The Co addition also improves free volume generation and higher delta H0 for ribbon, but lower amount free volume generation in bulk alloys (rod) than ribbon.