The long-term atmospheric corrosion behavior of extruded aluminum alloy 7075-T6 (UNS A97075) was investigated by weight loss, corrosion morphology, loss in mechanical properties, and corrosion products in field testing that lasted more than 20 years. The results demonstrated that extruded 7075-T6 exposed for 20 years suffered obvious exfoliation and intergranular corrosion in coastal atmospheres, and that their mechanical properties drastically decreased. In industrial and coastal-industrial atmospheres, weight losses for extruded 7075-T6 were high and the corrosion products were mainly aluminum sulfate hydroxide hydrates (Al 2 SO Extruded 7075-T6 was tested in this study. The chemical composition of the test materials is provided in Table 1. The extruded 7075-T6 was angle-shaped; the size of the sample was 200 mm long by 3.0 mm thick. The three-dimensional microstructure of the partial specimen is shown in Figure 1. The S direction refers to the through-thickness direction, and the L direction runs along the direction of extrusion. A coarse-grain microstructure (about 40 μm in thickness) appeared on the surface layers in the T and L sections, and the grains beneath this microstructure were highly elongated and flattened. The morphology and composition of precipitated phases of 7075-T6 were also investigated ( Figure 2). According to the energy-dispersive spectroscopy (EDS) results and the relevant literature, the S phase (Al 2 CuMg) and T phase (AlZnMgCu) typically were found in the Al 7075-T6 material (Figures 2[a] and [b]).The exposure tests were performed at the Beijing, Jiangjin, Qingdao, Guangzhou, Qionghai, and Wanning test sites. The geographic coordinates of the test sites and essential environmental characteristics during the period from 1984 to 1994 are given in Tables 2 and 3, respectively. In Beijing, the concentration of sulfur dioxide (SO 2 ) is 44.2 mg(cm 2 d) -1 and that of Clis very low. The average relative humidity (RH) is 57% so the test site has an urban atmosphere. In Jiangjin, the concentration of SO 2 is 66.7 mg(cm 2 d) -1 and that of Clis very low; therefore, the test site has an industrial atmosphere with a pH of approximately 4.4. The Qingdao, Guangzhou, Qionghai, and Wanning test sites are located approximately 34 m, 100 km, 20 km, and 350 m from the coast, respectively, and the average amount of sea salt particles in those atmospheric environments was 12.1, 11.2, 4.9, and 0.9 mg(cm 2 d) -1 , respectively. Furthermore, in Qingdao, the concentration of SO 2 was 70.4 mg(cm 2 d) -1 . At the Qionghai and Wanning test sites, the monthly average RH and tem-

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[1][2][3] . Semisolid slurry preparation is one of the most critical steps for semisolid casting, and its primary goal is to prepare slurry with uniformly distributed fine globules. Among various methods [4][5][6][7] of semisolid slurry preparation, electromagnetic stirring (EMS) is particularly attractive as the stirring intensity can be easily controlled and the melt is free of pollution [8][9][10] . However, the slurry primary phase in a large diameter maker (hereafter referred to as large volume slurry) is hard to be refined and homogenized due to the sharp decrease of electromagnetic force from the Abstract: Slurry preparation is one of the most critical steps for semisolid casting, and its primary goal is to prepare slurry with uniformly distributed fine globules. In this work, electromagnetic stirring (EMS) and the addition of Sc and Zr elements were used to prepare semisolid slurry of 7A04 aluminum alloy in a large diameter slurry maker. The effects of different treatments on the microstructure, composition and their radial homogeneity were investigated. The results show that, compared to the slurry without any treatment, large volume slurry with finer and more uniform microstructure can be obtained when treated by EMS, Sc, or Zr additions individually. EMS is more competent in the microstructural and chemical homogenization of the slurry while Sc and Zr additions are more excellent in its microstructural refinement. The combined treatment of EMS, Sc and Zr produces premium 7A04 aluminum alloy slurry with uniformly distributed fine α-Al globules and composition. The interaction mechanism between EMS and Sc and Zr additions was also discussed. periphery to the interior [11,12] . Scandium (Sc) and zirconium (Zr) are potent grain refiners for Al alloys [13,14] . With the addition of Sc and Zr elements (hereafter referred to as GR), numerous heterogeneous nuclei can be formed in Al alloy slurry, which also can contribute to the refinement and homogeneity of the slurry microstructure. For these reasons, the compound treatment including EMS, Sc and Zr additions is supposed to obtain large volume slurry with well dispersed fine primary α-Al globules. In this research, the effect of combined treatment of EMS, and Sc and Zr additions on the microstructure and the homogenizing of aluminum alloy large volume slurry was investigated.

To analysis the microstructure and properties of super-high strength Al-Zn-Mg-Cu alloys containing Zr ,Ni and Mn, the apparatus of SEM、TEM、and Tensile machine was used. The results show that the microstructure was fine and homogeneous, the phases became finer for the alloys with adding Zr, Mn, Ni than the alloy with Zr only after solid solution. The ultimate tensile strength of the alloy was 850MPa and the elongation was 5% respectively at peak aging.

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