Atomic-scale quasi in-situ TEM observation on the redistribution of alloying element Cu in a B4C/Al composite at the initial stage of corrosion

The present study reports an atomic level quasi in-situ TEM observation of the redistribution of alloying element Cu in the corrosion process of a B4C-reinforced Al-Mg-Si-Cu composite. Cu atoms were found to combine with Mg and form a thin layer at the interfaces between the aluminum matrix and nano-reinforcements (i.e. Mg(Al)B-2 and Al3BC). Dealloying of the Cu/Mg-rich layer was revealed. The following decomposition of Mg(Al)B-2 resulted in narrow corrosion trenches forming around Mg(Al)B-2 and then the localized pitting of the matrix. In addition, the liberated Cu ions were then redeposited and formed noble Cu nano-particles upon cathodic Mg(Al)B-2 and B4C particles.