Microstructure And Properties Of Al-Si-Zn-Mg-Cu Alloy Based On Direct Chill Casting

Aluminum-silicon (Al-Si) alloys are widely applied in aeropace, automobile and electronic industries due to their excellent wear and corrosion resistance, low density, low coefficient of thermal expansion and good strength and castability. However, due to the brittle silicon is prone to crack, Al-Si alloys experience low performance. In this paper, the microstructures of Al-Si-Zn-Mg-Cu direct chill (DC) cast is studied, and alloy phase composition and distribution is analysed. The characteristics of the alloy organization after extrusion is observed at the same time, the structure and mechanical properties has been studied under diffirent heat treatment process, this paper also discusses the influences of aluminum alloys on Al, Zn, Mg, Si, Cu elements. The following conclusions may be drawn from the results of the present investigation.1. In Al-Si eutectic structure, α-Al、Si、Mg2Si、Al2Cu、Al5Cu2Mg8Si6and Al8FeMg3Si6are observed in DC cast Al-13Si-5Zn-2.5Mg-1.6Cu alloy as well as DC cast Al-15Si-5Zn-2.5Mg-1.6Cu. Al-15Si-5Zn-2.5Mg-1.6Cu alloy has more primary silicon than Al-13Si-5Zn-2.5Mg-1.6Cu alloy. There is no Zn phase in cast microstructure, and Zn all dissolve into a-Al, make an effect of strong solid solution intensification.2. These two kinds of alloy extrusion organization and mechanical properties are not significant. The equiaxed grains are elongated to fibrous form along deformation direction after extrusion, The second phase is obviously reversed to the extrusion direction.After extrusion, the tensile strength is about310MPa, the elongation is about7%.3. To study the heat treatment process,this work makes different aging temperature and time. After solution treatment at500℃for4h,and aging treatment at160℃for4h, Mechanical properties of the alloy is the best, the Vickers hardness is230.75, the tensile strength is about395.87MPa, which has been stepped up31per cent, the yield strength is263.76MPa,but the extensibility reduced to3%. In the same conditions, the tensile strength and yield strength of Al-13Si-5Zn-2.5Mg-1.6Cu alloy is better than Al-15Si-5Zn-2.5Mg-1.6Cu alloy. With the increase of aging time, the mechanical properties of alloy show a steady decline trend.