Effect of Cu addition on microstructure and corrosion behavior of Al-15Mg2Si composite

The Cu effect on the microstructure and corrosion resistance of Al-15Mg(2)Si composites was studied. The results showed that Cu addition decreased the average size of primary Mg2Si (Mg2SiP) particles, changed the hopper-like Mg2SiP particles to polyhedrals, and caused the formation of ?-Al2Cu and Q-Al5Mg8Si6Cu2 compounds in the composite matrix. According to the image analysis results, increasing the Cu content from 0.01 to 5 wt% halved the average size of Mg2SiP particles, increased their fraction by about 40 %, and increased the composite porosity content. The electrochemical impedance spectroscopy showed that adding 5 wt% of Cu resulted in an increase of about 3.7 times in the corrosion resistance as compared to Al-15Mg(2)Si composite. The beneficial effects of Cu were also confirmed by the potentiodynamic polarization experiments. Cu addition seems to promote less intense general corrosion than the base alloy's localized attack.