Diffusion of Au and Cu in amorphous Fe80B20 and Fe82B18 alloys

Abstract

Diffusion rates (D) of Au in two amorphous alloys, Fe80B20 and Fe82B18, and of Cu in amorphous Fe82B18 alloy were measured in the temperature range 546–645 K by using the technique of Rutherford backscattering spectrometry (RBS) and Auger electron spectroscopy (AES), respectively. The diffusion of Au was found to be ∼3 to 6 times faster in Fe80B20 than in Fe82B18, though both the alloys had almost similar crystallization temperatures. The observed differences in the diffusion rates corroborate the fact that Fe80B20 has a more open structure than Fe82B18 as revealed from the reported values of the metal packing fractions of these two alloys. Also, the diffusivities of smaller sized Cu atoms (radius: 0.128 nm) were found to be higher by more than an order of magnitude than those of larger sized Au atoms (radius: 0.146 nm), suggesting a dependence ofD on the size of the diffusing species.