The Effect of Zn Incorporation on the Structure and Mechanical Properties of the Al-Zn Alloy System

A series of Al-xZn alloys (x = 0-30 wt.%) were prepared to investigate the effect of Zn on their structure and mechanical properties. The alloys with Zn content ranging from 0 to 10 wt.% were consisted of single alpha-Al solid solution phases, but when more than 20 wt.% was added, typical dendritic/interdendritic structure formed and was composed of alpha-Al phase/Zn-rich (eta-rich) phase and alpha + eta eutectoid structure. The grain size of the alloys decreased first and then increased as the Zn incorporation increased. The optimal average size of the refined grain was 122 +/- 32 mu m in the Al-20 wt.% Zn alloy due to the high drag pressure and low grain boundary growth rate caused by the segregation of Zn atoms and the grain boundary pinning by Zn nanoparticles (eta-PP). Moreover, the Al-20Zn alloy demonstrated balanced strength and reasonable ductility and the main strengthening mechanism mainly relied on boundary strengthening by grain refinement.