Peritectic Structure Evolution in Hot-dip Zn-Al Alloy Coatings

The present study investigated the microstructure in hot-dip Zn-(11, 22, 30)%Al coating steel sheets in order to clarify their solidification microstructure evolution process. There are two kinds of Zn-Al binary phase diagrams. One includes peritectic reaction but another doesn't. In the Zn-Al binary phase diagram including peritectic reaction, the peritectic reaction occurs when the Al content is higher than 13%. In fact, the peritectic structure was formed in dendrites of the hot-dip Zn-(22, 30)%Al coating steel sheets, but not in the hot-dip Zn-11%Al coating steel sheets. This indicates that the Zn-Al binary phase diagram including peritectic reaction is suitable for understanding the solidification microstructure evolution of hot-dip Zn-Al alloy coating steel sheets.