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SEMISOLID metal (SSM) formation, including thixoforming and rheocasting, has been recognized as a promising technology and has received considerable interest because components produced by this novel technology have various advantages over conventional castings.[1] Rheocasting involves treating the solidifying alloy to obtain nondendritic semisolid slurry, and then shaping the slurry directly. A number of processes has been developed to prepare semisolid slurry. Recently, the indirect ultrasonic vibration (IUV) method, in which the horn is vibrated under the outside of the metallic cup containing molten alloy, has been developed for preparing semisolid slurry. Previous studies have shown that the slurries prepared by this method have fine and globular grains, and the IUV process has advantages over some SSM processes in terms of melt degassing, increased homogeneity, and technological flexibility.[2,3] Die casting (DC) is one of the most common methods adopted for shaping semisolid slurry. Intense shear during injection reduces the viscosity of the slurry and is favorable to mold filling, but the slurry is inclined to experience turbulent flow. Therefore, semisolid components produced by DC usually contain low level porosity, rather than no porosity.[4] Alternatively, squeeze casting (SC) can compensate the shortcomings of DC and produces high-integrity components. SC combines casting and forging process into a single SHULIN LU¨, Postdoctoral Student, SHUSEN WU, Professor, and LI WAN and PING AN, Associate Professors, are with the State Key Lab of Materials Processing and Die and Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, P.R. China. Contact e-mail: [email protected] Manuscript submitted July 3, 2012. Article published online February 12, 2013 METALLURGICAL AND MATERIALS TRANSACTIONS A

operation where the melt is injected steadily and solidifies under a high pressure.[5] In the absence of high speed and intense shear, lower filling ability of the slurry is expected in SC, and it restricts the complexity of the components that can be produced by this process. But its slow injection and high pressure can eliminate the porosity and bring excellent mechanical properties. The widely used Al alloys for SC are conventional Al-Si cast alloys and certain heat-treatable wrought Al alloys such as 2xxx, 6xxx, and 7xxx series.[6–10] Studies on SC of 5xxx series wrought Al alloys are very few. Lee et al. studied the microstructure characteristics and cooling behavior of 5083 Al alloy produced by traditional SC,[11,12] but no study has been reported on SC of semisolid 5xxx Al alloys. The 5xxx series alloys have found a large variety of applications including architecture, household appliances, marine craft, and automotive body sheet due to their excellent weldability and corrosion resistance.[13] They are typically used for thinplate rolling. However, it is hard for traditional plastic forming technologies to process components with complex shape. Rheocasting may solve this problem. We hav