The corrosion behavior of amorphous and nanocrystalline Fe_(73.5)Cu_1Nb_3Si_(15.5)B_7 alloy

摘要

The potentiodynamic polarization curves in 0.5 M NaCl solution before and after crystallization of Fe_(73.5)Cu_1Nb_3Si_(15.5)B_7 alloy have been studied in relation to the microstructure and alloy composition. It was shown that the corrosion resistance of the alloy strongly depending on these two factors. The observed decrease in corrosion resistance of the alloy after the heat treatment up to 480 ℃ in comparison to the corrosion resistance of the alloy in the as prepared state is attributed to the increased inhomoge-neity of the alloy that coincides with the first appearance of Fe_3Si phase. Further heating (up to 600 ℃) resulted in an increase in the number of Fe_3Si nanocrystallites and the appearance of a FeCu_4 phase. After annealing at 600 ℃ the lowest corrosion rate, 0.004 mm a~(-1), was observed. Annealing of the samples at higher temperatures (>600 ℃) induced formation of six crystalline phases which proved detrimental to the corrosion resistance of the Fe_(73.5)Cu_1Nb_3Si_(15.5)B_7 alloy. Solid corrosion products were identified on the surface of the samples after anodic polarization.