Length scale of solidification microstructure tailoring corrosion resistance and microhardness in T6 heat treatment of an Al–Cu–Mg alloy.

Abstract

The combined effects of solidification microstructure refining scale and T6 heat treatment conditions on corrosion behaviour and Vickers microhardness of an Al–3 wt-% Cu–0.5 wt-% Mg alloy were studied. Then, representative samples having quite distinct primary dendritic spacings were solution treated at 495°C for 3 h and artificially aged at 200°C during different times. It was found that the feature of finer solidification microstructure having higher corrosion current density and higher microhardness can be inherited to subsequent T6 heat treatments. In contrast to the as-cast condition, the aging times of 0.5 and 1 h were shown to promote lower corrosion rates without corrosion occurring at the central region of Al-rich matrix. On the other hand, the aging time of 3 h led to a significant decrease in both the corrosion resistance and the microhardness. Finally, a comparative analysis with other works from the literature was also conducted.