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Semi-solid metal (SSM) casting of aluminum components is currently establishing itself as a viable process for critical applications in the automotive industry. SSM casting processes compete favorably on both cost and performance with other casting techniques including gravity permanent mold (GPM), conventional high pressure die casting (HPDC) and squeeze casting. In this paper the various SSM casting routes in use today are reviewed. The two categories of SSM processes are thixocasting (involves the use of electro-magnetically stirred or grain-refined billets) and rheocasting (slurry produced directly from the liquid phase). The former requires a billet that needs to be reheated and processed, whereas the latter is cast directly from the liquid state. Also described here are new approaches to slurry making. These include the Slurry on Demand (SoD) process from AEMP, the Sub Liquidus Casting (SLCR) process from THT, and Diffusion Solidification.

This paper provides a description of commercially available die casting processes including conventional die casting process (high pressure, high velocity), squeeze casting (high pressure, controlled cavity fill rate), semi-solid metal casting, and Vacural™ (a variation of the conventional die casting process). The various automotive products made using these processes are also reported in the study. In this study, the mechanical (tensile, impact, fatigue strength and fracture toughness) and wear properties are compared among the above processes. Results indicate that mechanical and wear properties of aluminum alloys made using the “high integrity” casting processes (squeeze, semi-solid metal casting and Vacural™) are superior to those of conventional die castings.