Effects of the Aluminum Alloy with Intermetallic a Phase on the Microstructural and Corrosion Resistance

Abstract

The aluminum alloy with intermetallic α-Al 15 (Fe,Mn,Cr) 4 Si 2 phase with polygonal morphology, denoted by Al-α alloy was processed by controlled solidification and this alloy was studied in order to evaluate the microstructure, microhardness, corrosion resistance and electrochemical impedance when this alloy was immersed in an electrolytic medium at 0.1 mol/L solution of sulfuric acid.The intermetallic α-Al 15 (Fe,Mn,Cr) 4 Si 2 with polyhedron morphology presents a microhardness of 483 HV and being much higher than pure aluminum. The polarization resistance of the pure Al is much higher than Al-α alloy and the corrosion rate in pure Al is low, however, the corrosion rate in Al-α alloy is moderate. The Al-α alloy electrode presents a larger area of the voltammogram than the pure Al electrode and pure Al presents a larger region passivity, however, through Nyquist diagram, both samples presented the capacitive semicircle and inductance region. Being so, the polarization resistance was a lot bigger in pure Al than the Al-α alloy, and these results were similar to result of micro polarization. This alloy is suitable for use in many automotive applications increasing lifetime of its components, due to, it has low density, high microhardness and in sulfuric acid medium has noble behavior and presents a good corrosion resistance, and a low corrosion rate.