Effect of Zn and Cu Addition on Microstructure and Mechanical Properties of Al-10wt%Mg Alloy

Abstract

5xxx series aluminum alloys have been widely used in automobiles, ships, aerospace and other fields for their low density, good corrosion resistance and weldability. The present study designs a new Al-10.0Mg-1.0Zn-0.15Cu (wt%) alloy with different composition from the traditional 5xxx series and 7xxx series aluminum alloys; the Zn/Mg ratio is below 1.0. Detailed characterization by scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM) has been carried out to reveal the microstructural evolution. The results show that the addition of Zn and Cu inhibits the precipitation of the Al3Mg2 phase in the traditional Al-Mg binary alloy during annealing and promotes the precipitation of T-Mg32(Al,Zn)49 phase, which contributes to precipitation strengthening. After 75% rolling and 150 °C annealing, the T-Mg32(Al,Zn)49 phase precipitates and the alloy obtains good strength and plasticity coordination with 0.2% offset yield strength of 519 MPa and ultimate tensile strength of 653 MPa, accompanied by uniform elongation of 8.1%. The mechanisms underlying the improved strength and plasticity in the Al-10.0Mg-1.0Zn-0.15Cu (wt%) alloy are discussed.