Effects of trace amounts of Zr and Sc on the recrystallization behavior and mechanical properties of Al-4.5Zn-1.6Mg alloys

•The Al-4.5Zn-1.6Mg alloys without the Zr and Sc addition obtained a coarse grain.•The addition of Zr can effectively restrict grain growth, producing Al3Zr precipitates to obtain a mainly equiaxial grain.•The addition of Sc led to better inhibition to recrystallization through fine precipitates of coherent Al3Sc particles. The effects of Zr and Sc on the recrystallization behavior and mechanical properties in Al-4.5Zn-1.6Mg alloy were investigated to understand the strengthening mechanism and to improve the mechanical properties. The results show that the Al-4.5Zn-1.6Mg alloys without the Zr and Sc addition obtained a coarse grain structure; the addition of 0.1% Zr to the Al-4.5Zn-1.6Mg alloy, made it possible to inhibit the grain growth; the addition of 0.1% Sc led to better inhibition to recrystallization through fine precipitates of coherent Al3Sc phases. The precipitation of coherent Al3Sc particles acted to strongly pin the grain boundaries, thereby effectively restraining their migration leading to the higher strength of the Sc-containing Al-4.5Zn-1.6Mg alloy.