The Microstructure And Mechanical Properties Of Zinc In Al-Si-Cu-Mg Alloy

In view of strengthening traditional structural materials,the development cast of aluminum alloy with excellent formability of the high-intensity,high toughness and low-cost is of important scientific significance and practical value.Many domestic and international research institutes are using the methods that add zinc to enhance aluminum alloy,and develop various aluminum alloy of high mechanical properties.In this paper, SEM,DSC and TEM analysis test methods have been used to trace the elements Zn in Al-Si-Cu-Mg cast alloy.Mechanical properties test results show that when the addition of Zn within 0.1%～1.0%(wt%),Zn can increase the hardness and enhance the hardening rate of alloy. With Zn add the tensile strength increases slightly and elongation is gradually reduced. Zn can improve the peak hardness,speed up the hardening rate.Age hardening curve shows that:alloy presents hardening phenomenon as usual, after a certain period of time the alloy hardness improves significantly,and then softens.Microstructure analysis shows that Zn does not exist in a form of phase but as solid solution in the form of relatively uniform distribution in the matrix thus leads to promote Al₂Cu phase distribution during heat treatment process,so that the hardness of alloy increased.Through DSC and TEM analysis shows that the addition of zinc cause the precipitation sequence in:1.Zn promotes the formation aging process for GPâ…¡zone and accelerates the age-hardening rate;2.Stable phase is no longer formed.TEM results show that the addition of Zn can increase GPâ…¡zone in the number of nucleation and reduce the growth rate.Zn has higher vacancy binding energy,the large number of vacancies are captured by Zn atoms so that Cu atoms in alloy,such as,the diffusion of solute atoms' vacancies drop sharply,and hampers the GPâ…¡zoneθ"phase of growth.