Corrosion and wear resistance of hypoeutectic Zn–Al alloys as a function of structural features

The aim of the present research was to investigate the role of the type of grain macrostructure (columnar, columnar-to-equiaxed transition–CET -, and equiaxed) and microstructure (secondary dendrite arm spacing - λ2) in the wear and electrochemical behavior of hypereutectic Zn–Al alloys (Zn-1wt%Al, Zn-2wt%Al, Zn-3wt%Al and Zn-4wt%Al) directionally solidified in a vertical upward directional solidification device. We also aimed to, correlate the thermal parameters with the electrochemical and wear properties. The results obtained in this alloy system indicate that the corrosion resistance decreases as the concentration of aluminum increases, but that at the highest concentrations (near the eutectic concentration) this resistance depends on the structure. For the same wear conditions, the wear rate of the equiaxed region is lower than the columnar and transition regions. Independently of the type of structure, wear resistance increases as the aluminum concentration increases. For each alloy concentration, the wear resistance increases from the columnar to the equiaxed structure. A clear inverse relation is observed between the wear resistance and λ2, which may explain the increase in wear resistance in the equiaxed region. At low spacings, the wear rate converges to a single value.
Highlights ► A combined study encompassing the grain and dendritic scale was here performed. ► The results include corrosion as well as wear parameters. ► Even at the highest Al wt%, the corrosion resistance depends on the structure. ► The wear resistance increases from the columnar to the equiaxed structure. ► A clear inverse relation is observed between the wear resistance and λ2.