Effect of quenching protocols on microstructure and corrosion morphology in a recycled Al–Mg–Si alloy: Tracing Cu impurities

In the present work, three different quenching protocols - water quenching (WQ), forced air quenching (FAQ) and air quenching (AQ) - were utilized to tailor the intragranular and intergranular preference of Cu impurities in a recycled AA6082 alloy. It is found that Cu tends to be incorporate in the precipitates at grain boundaries in the WQ-treated alloys. However, both AQ and FAQ protocols interestingly eliminate such intergranular Cu enrichment, consequently sequestering Cu solutes in (Mg, Si)-rich precipitates in grain interiors. As the quenching rates decrease, the FAQ- and AQ-treated alloys resultantly exhibit a positive shift in pitting potential, which is accompanied by a transition in corrosion morphology from boundary attack to pitting, with a notable reduction in corrosion depth.