Comparison of the Oxidation Process in Pure Iron and Diluted Fe\u2013Si Alloys: A Transmission M\xf6ssbauer Spectroscopy Study

Abstract

The room temperature study of polycrystalline iron, Fe0.99Si0.01 and Fe0.97Si0.03 alloys, was performed using the 57Fe transmission Mössbauer spectroscopy (TMS). The TMS measurements allow us to determine changes of chemical composition and content of iron oxides in the studied samples during exposure to air at 570, 870 and 1070 K. The results indicate that the chemical composition of samples changes significantly and it is strongly dependent on the temperature at which the studied samples are exposed to air. Moreover, it was shown that the addition of few atomic percent of Si impurities to iron leads to a significant slowdown of the internal oxidation process. The iron and silicon internal oxidation kinetics for Fe0.99Si0.01 and Fe0.97Si0.03 alloys were calculated using the Deal-Grove model. The activation energies EA for the internal oxidation of iron atoms in studied Fe–Si alloys were estimated: EA = 1.46 (3) eV for Fe0.99Si0.01 and EA = 1.62 (6) eV for Fe0.97Si0.03.