Al-Fe 合金の耐孔食性に及ぼす巨大ひずみ加工 HPT 処理の影響

概要

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The effects of reducing the grain size by high-pressure torsion (HPT) on the pitting corrosion resistance of Al-Fe alloys with Fe contents of 0.5, 2, and 5 mass% were investigated by means of polarization curves in solutions containing 0.1 mol•dm−3 Na2SO4 and 8.46 mmol•dm−3 NaCl (300 ppm Cl−) at 298 K and by surface analysis. The potentials for pitting corrosion of the Al-Fe alloys were clearly shifted to the noble direction by HPT, leading to an improvement in pitting corrosion resistance. This improvement was larger in the Al-0.5%Fe and Al-2%Fe alloys and smaller in the Al-5%Fe alloy. The Al-Fe alloys contained precipitates of Al-Fe intermetallic compounds, around which pitting corrosion occurred. The Al-5%Fe alloy, in particular, contained large precipitates tens of micrometers in size, and pitting corrosion was significant around these large precipitates. It is evident from the time-dependence of the corrosion potential and the polarization resistance of the corrosion reaction that the formation rate of Al oxide films increases as a result of HPT. It was therefore concluded that the improvement in pitting corrosion resistance of the Al-Fe alloys with HPT is caused by increasing the oxidation rate of Al.
日本金属学会 ; 1937-の論文