Aluminum-zinc alloys are cheaper than aluminum-copper alloys, with equal mechanical properties, but less corrosion-resistance. On the other hand, zinc-aluminum alloys was technologically progressive for gravity casting, competing with bronze, cast iron and aluminum. The mechanical properties of these alloys are very important for different applications.
In the present work, diluted Al-Zn (Al-2wt.%Zn and Al-4wt.%Zn) and Zn-Al (Zn-2wt.%Al and Zn-4wt.%Al) alloys were solidified directionally upward, obtaining the columnar-to-equiaxed grain transition (CET) phenomenon. Through the measurement of the temperature profiles during solidification, the thermal parameters (cooling rates, temperature gradients and interphase velocities, local solidification times) were determined. After that, the grain structure of the specimens was observed from the chill to the top of the specimens, and correlating with the macro segregation of principal constituents of alloys (Al and Zn) along the specimens. In addition, microhardness measurements in different grain zones of the specimens, in the columnar (at the bottom), CET and in the equiaxed grain zone (at the top) were done. The results obtained in different alloys and grain structures were analyzed.