Effect of Yb microalloying on microstructure and properties of Al-Zn-Mg-Cu alloy

Abstract:

Al-Zn-Mg-Cu and Al-Zn-Mg-Cu-Yb alloys were prepared by melting casting and hot extrusion. The effect of rare earth Yb microalloying on the microstructure of Al-Zn-Mg-Cu alloy was observed by optical microscope, scanning electron microscope and transmission electron microscope, and the properties were tested by differential thermal analyzer, tensile tester and electrochemical workstation. The results show that the addition of Yb can obviously refine the grains, and the microhardness and tensile strength increase from 125.6 HV and 562.9 MPa to 154.9 HV and 616.3 MPa respectively. The tensile fracture mode also changes from intergranular and dimple coexisting mixed fracture to complete dimple fracture. However, the precipitation of coarse Al8Cu4Yb phase in the matrix and the continuous distribution of η phase on grain boundary are unfavorable to the corrosion resistance.

Key words:Al-Zn-Mg-Cu-(Yb) alloy; refine grains; tensile fracture; corrosion resistance