The corrosion resistance of FeSiBPNbCu bulk metallic glasses in sulphuric acid solutions

In this paper, the alloying effects of minor Cu on the relationship between microstructure and corrosion resistance of (Fe0·76Si0·09B0·1P0·05)99 − xNb1Cux (x = 0, 0·25, 0·5, 0·75, 1) ferromagnetic bulk metallic glasses (BMGs) were investigated in details. The microstructure characterisation has revealed that the introduction of proper Cu elements leads to the presence of α-Fe clusters in the as-cast amorphous rods. In addition, α-Fe nanocrystals with a suitable size and volume fraction can accelerate the formation of the protective passive layers at nanocrystals/amorphous interfaces, and lead to the improvement of corrosion resistance. However, when the Cu content x exceeds 0·75, the corrosion resistance of the FeSiBPNbCu BMGs reduces significantly. All the results imply that the Cu content plays a key role in the characteristic size of α-Fe nanoparticles embedded in the glassy matrix, and there is a dependent correlation between the corrosion resistance and the microstructure.