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 Si composites was studied. The results showed that Cu addition decreased the average size of primary Mg Si (Mg Si ) particles, changed the hopper-like Mg Si particles to polyhedrals, and caused the formation of -Al Cu and -Al Mg Si Cu 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 Mg Si 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 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.