Effect of Er/Sc-Zr Microaddition on Microstructure and Properties of Hot-rolled Al-5Mg-3Zn Alloy

Microalloying elements of Zr（0.1wt%）-Er（0.2wt%）and Zr（0.1wt%）-Sc（0.2wt%）were added to Al-5Mg-3Zn alloys, and Al-5Mg-3Zn-0.2Er-0.1Zr, Al-5Mg-3Zn-0.2Sc-0.1Zr alloys were obtained. The three alloys were hot rolled. The effects of microalloying elements on the microstructure, tensile properties and corrosion resistance of alloy were studied. The results show that the addition of Zr-Er or Zr-Sc elements could retain more deformed structures and inhibited the dynamic recrystallization of the alloy in hot rolling, and the inhibition effect of Zr-Sc elements was stronger than that of Zr-Er elements. A small number of large T phases appeared in Al-5Mg-3Zn hot-rolled alloys. In addition to T phases, Al₃（Er, Zr）and Al₃（Sc, Zr）phases also existed in Al-5Mg-3Zn-0.2Er-0.1Zr and Al-5Mg-3Zn-0.2Sc-0.1Zr hot-rolled alloys, respectively. There was no precipitated phase or precipitated zone at grain boundaries of the three test alloys. Compared with those of Al-5Mg-3Zn hot-rolled alloy, the tensile strength and yield strength of Al-5Mg-3Zn-0.2Er-0.1Zr hot-rolled alloy were increased by 9.3% and 34.3%, respectively, and that of Al-5Mg-3Zn-0.2Sc-0.1Zr hot-rolled alloy increased by 24.8% and 35.6%, respectively. All three hot-rolled test alloys maintained good corrosion resistance, and Al-5Mg-3Zn hot-rolled alloy had better corrosion resistance.