A fluctuation electron microscopy study of metallic glasses

Al85Ni5Y10-xCox (x = 0, 2) and Cu46Zr54-xAlx (x = 0, 7) metallic glasses (MGs) have been examined using fluctuation electron microscopy (FEM). Strong medium-range order (MRO) was revealed in both MG systems, by peaks in intensity variance curves. Minor changes in composition result in differences in these peaks, while diffraction patterns remain identical. Specifically, minor alloyings of Co into the Al85Ni5Y10 and Al into the Cu46Zr54, forming Al85Ni5Y8Co2 and Cu46Zr47Al7 MGs, render the medium-range structure more homogeneous. This is in a good agreement with the increase of glass-forming ability in the two systems. This result sheds light on FEM as a useful tool to totally sense the structural changes in the medium range, helpful to study the effect of sample composition on properties of metallic glasses.