Study on ultrahigh strength Al-Zn-Mg-Cu alloy sheet
The effects of super high Zn,Mg content and trace Sc,Sm rare earch elements on microstructure and mechanical properties of Al-Zn-Mg-Cu alloy sheets have been studied,with metallographic microscope,scanning electron microscope and tensile testing machine.The results show that the strength increases as Zn and Mg content rises.The addition of trace Sm element doesn't affect grain refinement and forms Sm-contained second phase in the ma-trix that can not be eliminated and is to unfavorable properties.Sc can refine grains effective-ly,inhibit recrystallization and improve strength.The yield strength and tensile strength in-creases by 59 MPa and 51 MPa accordingly with addition of 0.2%Sc.The combined addi-tion of w(Zr)=0.12%and w(Sc)=0.2%on the basis of high alloying sheet results in yield strength of 726 MPa and tensile strength of 752 MPa.
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