Effect Of Zr、Cr And Yb Additions On Microstructure And Properties Of Al-Zn-Mg-Cu Alloy

Abstract:In order to meet the requirements of lightweight and high performance in the aerospace and other transportation, the development of Al-Zn-Mg-Cu alloys with super strength, high toughness and corrosion resistance properties are the goal of aluminum research. However, super strength has a negative effect on the properties of high toughness and corrosion resistance in aluminum alloys, It is necessary to develop new Al-Zn-Mg-Cu alloys with super strength, high toughness and corrosion resistance properties.The effects of Zr or Zr-Cr-Yb additions on recrystallization, mechanical properties and corrosion properties of Al-8.54Zn-2.41Mg-2.2Cu aluminum alloys, the effects of copper content on microstructure and properties of Al-8.54Zn-2.41Mg-xCu-0.16Zr-0.18Cr-0.3Yb aluminum alloys, the effects of Cr content on microstructure and properties of Al-8.54Zn-2.41Mg-1.3Cu-0.16Zr-xCr-0.3Yb aluminum alloys have been investigated by optical microscopy(OM),SEM, TEM, EDX analysis and mechanical properties and corrosion test (Intergranular corrosion, Exfoliation corrosion, SCC).The results are showed as follows:(1) The effects of Zr or Zr-Cr-Yb additions on microstructure and properties of Al-8.54Zn-2.41Mg-2.2Cu aluminum alloy have been investigated. Al-8.54Zn-2.41Mg-2.2Cu alloy,δb=524.7MPa, δ0.2=524.7MPa,δ=5.1%, KIC=19.4MPa-m1/2,ISSRT=0.156. Al-8.54Zn-2.41Mg-2.2Cu-0.16Zr alloy, δb=672.3MPa,δ0.2=643.6MPa,δ=10.1%, KIC=27.8MPa·m1/2,ISSRT=0.105. Al-8.54Zn-2.41Mg-2.2Cu-0.16Zr-0.18Cr-0.3Yb, δb=692.3MPa, δ0.2=643.8MPa,δ=10.5%, KIC=32.4MPa·m1/2,ISSRT=0.069. Al-8.54Zn-2.41Mg-2.2Cu-0.16Zr alloy has been partial inhibiting recrystallization by formed Al3Zr dispersoid with cubic L12-structure. The Al-8.54Zn-2.41Mg-2.2Cu-0.16Zr-0.18Cr-0.3Yb alloy with the highest overall performance has been inhibiting recrystallization more efficiently and aging precipitates have been distributed evenly by formed dispersoids with cubic L12-structure.(2) The effects of Cu content on the microstructure and properties of Al-8.54Zn-2.41Mg-xCu-0.16Zr-0.18Cr-0.3Yb aluminum alloy have been investigated. With the Cu content reduced from2.2wt.%to1.3wt.%, the volume fraction of residual eutectic phase decreases, the mechanical properties increase and the corrosion resistance first increases and then decreases.The optimum comprehensive properties of Al-Zn-Mg-Cu-Zr-Cr-Yb alloys were obtained by the Cu=1.3wt.%.(3) The effects of Cr content on dispersoids behavior and the microstructure and properties of Al-8.54Zn-2.41Mg-1.3Cu-0.16Zr-xCr-0.3Yb aluminum alloy have been investigated. Compared with Al-8.54Zn-2.41Mg-1.3Cu-0.16Zr-0.3Yb alloy, the number of dispersoids with cubic L12-structure of Al-8.54Zn-2.41Mg-1.3Cu-0.16Zr-0.09Cr-0.3Yb alloy increases and effectively inhibit recrystallization. The number of incoherent Al18Cr2Mg3dispersoids increases with the content of0.18wt.%Cr, which maybe decrease the upper limit of solution temperature,and making the burning phenomenon of alloy appeared in the solution process, and the alloy comprehensive performance decreases.