Effect of Zr addition on the precipitation in Mg–Zn-based alloy

The minor alloying element Zr in a Mg–6.2Zn–0.6Zr (ZK60) alloy causes the formation of fine Mg(Zn,Zr) precipitates at 350 °C which play a critical role in dynamic recrystallization during extrusion and hot rolling. When the alloy is artificially aged at 160 °C, the β1′-precipitate grows in the [0 0 0 1] direction from the Mg(Zn,Zr) particles. The structure of the Mg(Zn,Zr) is exactly the same as that of β1′, indicating that Zr partitioning occurs only at elevated temperature due to the sluggish diffusion of Zr.