Glass forming ability, thermal stability, crystallization and magnetic properties of [(Fe,Co,Ni)0.75Si0.05B0.20]95Nb4Zr1 metallic glasses

Abstract

The variation in the glass forming ability, thermal stability, crystallization and magnetic properties of [(Fe60Co40−xNix)0.75Si0.05B0.20]95Nb4Zr1 metallic glasses with x=0 and 10at.% has been studied. The addition of Ni enhances the extension of the supercooled liquid region. Different criteria for the prediction of glass forming ability have been used leading to different conclusions due to the different parameter's dependence. However, it was experimentally observed that upon copper mold casting the Ni-free master alloy allows preparation of fully amorphous rods with the largest diameter. The structural evolution upon crystallization has been monitored using X-ray diffraction and Mössbauer spectroscopy. The results show the precipitation of the metastable Fe23B6-type phase as the primary crystallization product. The kinetic analysis using the Master Curve method leads to a value of the activation energy Ea=494kJ/mol and indicates a homogeneous nucleation and diffusion-controlled growth transformation. Further heating shows the formation of different Fe environments that give rise to stable phases in the fully crystalline samples. The magnetic properties as Curie temperature and saturation polarization are affected by the partial substitution of Ni but no significant effect was observed on the coercivity values.