Abstract
Two alloys containing different Mg contents have been used to study the combined effect of stirring and oxidation on microstructure and ductility. The results show that intensive stirring can sufficiently disperse the α-Al particles and enable better liquid feeding during solidification and consequently reduce the porosity. The morphology of the oxides is determined by the amount of both Mg and stirring. With lower Mg content, the oxides present as oxide films, which can be broken up during stirring. In alloy with higher Mg content, the oxides exist as particles with numerous cracks, and the particle size increases slightly after stirring. In the Magsimal 59 alloy, due to the presence of large clusters of pores in the fracture surface, the influence of the small oxide particles on the ductility is negligible. In contrast, in the 42000 alloy, large oxide films on the fracture surface are correlated with the ductility.
Highlights
Semisolid metal (SSM) casting has been widely used in automotive and electronic industries to achieve weight reduction.[1]
The results show that intensive stirring can sufficiently disperse the a-Al particles and enable better liquid feeding during solidification and reduce the porosity
A series of experiments have been performed to evaluate the effect of stirring on the microstructure and ductility of two different Al alloys containing different amounts of Mg
Summary
Semisolid metal (SSM) casting has been widely used in automotive and electronic industries to achieve weight reduction.[1]. The yield strength is heavily dependent on the solid fraction, particle morphology and particle distance,[7,8] and one effective approach to alter the particle distance is applying shearing to the slurry because of the Reynolds’ dilatancy.[9,10] in the RheoMetalTM process, it is possible to adjust the stirring method to obtain dispersed particles and globular particles in the slurry and, optimised casting microstructures. Another critical issue in SSM is the introduction of oxides during slurry preparation. The fracture surfaces from tensile test samples were analysed with scanning electron microscopy (JEOL JSM-7001F SEM) equipped with energydispersive x-ray spectroscopy (EDS) to evaluate the fracture mode and area fraction of both oxides and porosity in the fracture surface
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