Microstructure of As-Cast 7085 Aluminum Alloy by Homogenization

Abstract

7085 aluminum alloy has been widely used in aviation and aerospace because of high fracture toughness, high strength, slow quench sensitivity and low density. In the as-cast microstructure, it is not avoidable for massive un-dissolved secondary phases and dendritic segregation. The microstructure of as-cast high strength 7085 aluminum alloy after two-stage homogenization was studied by optical microscopy (OM), X-ray diffractometer (XRD), scanning election microscopy (SEM), energy dispersive spectrometer (EDS) and differential scanning calorimeter (DSC). It was found that the severe dendritic segregation exists in as-cast 7085 aluminum alloy and a small amount of Al7Cu2Fe exists in the as-cast 7085 alloy. The evolution of primary eutectic structure of 7085 alloy consists of three processes: the dissolution of non-equilibrium eutectic phase α (Al) + Mg (Zn)2, the transformation from Mg (Zn)2 to Al2CuMg and the dissolution of new phase Mg (Zn)2. A suitable two-stage homogenization scheme for as-cast 7085 aluminum alloy is 300°C/8 h + 465°C/24 h.