Effects of Sc and Zr addition on microstructures and properties of Al-Zn-Mg-Cu alloys

Two kinds of Al-Zn-Mg-Cu alloys with and without Sc and Zr were produced.The microstructure of the two alloys under different treatment conditions were studied by using optical microscope and transmission electron microscope(TEM).The mechanical properties and corrosion capability were investigated by cold tensile test,scanning electron microscope(SEM) and corrosion experiment.The results show that adding trace Sc and Zr can greatly fine the grain size of the Al-Zn-Mg-Cu alloy ingots and obviously improve the tensile properties and corrosion resistance of the Al-Zn-Mg-Cu-Zr alloys.The alloy which adds with Sc and Zr has 110(N/mm~2) higher in tensile strength and 91 N/mm~2 higher in bend strength than the alloy without after T6 process,and its ductility also improves a little.