Effect Of Solution And Aging Process On Structure And Properties Of Al-Zn-Mg-Cu Alloy

With the increasing demand for lightweight production and life,“lightweight manufacturing”is appeared.As the representative of lightweight aluminum alloy,Al-Zn-Mg-Cu aluminum alloy has the characteristics of high strength,low density,good processing performance and strong corrosion resistance.This experiment took the self-designed Al-Zn-Mg-Cu aluminum alloy as the research object,through the metallographic microscope observation,the XRD map analysis,the SEM analysis,the TEM analysis,the hardness test,the room temperature tensile test and the tensile fracture surface SEM scanning analysis and so on,systematically studying the effects of solution and aging on the microstructure and mechanical properties of Al-Zn-Mg-Cu aluminum alloys.The influence of only Y?only Er?compositing Y and Er on the microstructure and mechanical properties of the alloy.The influence of Sr and Y on the mechanical properties of the alloy.Effects of different Zn/Mg ratios on microstructure and mechanical properties of alloys.The conclusions are as follows:(1)With the increase of solid solution time,the fine??phases in the crystal becomes needle-like,short rod-like and disc-like????phases with larger size.The precipitation phases transition at grain boundaries become smaller and the spacing of precipitation phase decreases.With the increase of the solution temperature,the precipitated phases in the crystal are further refined,and the PFZ becomes narrower.The alloy has the highest elongation of 17.7%under the solution process:465?/25 min.(2)With the extension of the secondary aging time,the recrystallization degree of the alloy increases,and the number of grains gradually increase and refine,thus improving the mechanical properties of the alloy.The secondary aging time continued to prolong,and the second phase particles gradually grow and coarsen,and the shape changed from disc-like shape to short rod-like shape and needle-like shape.The grain boundary precipitated phases(?phases)coarsen,at the same time,the spacing increases,the PFZ widens,the pinning effect on dislocations is greatly reduced,and the strength of the alloy decreases accordingly.The tensile strength,yield strength are 668.4MPa,624.45MPa,the elongation and Brinell hardness reach 10.3%,132HBW of the alloy under the secondary aging process:120?×3h+160?×5h.The alloy has the highest elongation of 20%under the aging process:120?×3h+160?×7h.The tensile strength,yield strength and Brinell hardness are 632.3MPa,569.46MPa,126HBW,respectively.(3)The order of refinement effect:add separately Y=compound add Y?Er>add separately Er,so,Al₆Cu₆Y has a better refining effect on the alloy.When the element of Y is added separately,the comprehensive mechanical properties of the alloy are the best.(4)With the Zn/Mg ratio increasing and the Cu element content added at the same time,the grains of the alloy are gradually refined,and the unbalanced solidification phases are gradually increased.The tensile strength,yield strength and elongation of Zn/Mg=5.8 alloy reach 552.72MPa?500.6MPa?12.13%respectively after the same solution and aging process.The alloy of Zn/Mg=5 has the best Brinell hardness,reaching 100.7HBW.