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Hypereutectic aluminum-silicon alloy 390 offers properties akin to a composite material exhibiting outstanding wear characteristics, excellent high temperature strength, a high modulus of elasticity and a low thermal expansion coefficient. These properties make 390 a promising candidate for heavy wear conditions. Liquid casting with 390, however, poses several problems thus making semi-solid processing an attractive alternative. In this study, a motorcycle sprocket was semi-solid metal (SSM) cast with A390. The resulting mechanical behavior and wear resistance was promising for parts that will undergo heavy wear applications. Use of this alloy in semi-solid production should prove to be an attractive alternative for automotive engineers.

Aluminum alloys are generally used in transportation-related applications where weight saving is of paramount interest. In addition to aluminum's density advantage related to other metals, weight can also be saved by the use of thin walled components. However, there are limited ways to make complex shape, thin walled, high integrity castings at high volumes. One such way is semi-solid metal (SSM) casting. In the past, minimum wall sections for semi-solid castings have been limited to the range of 2 to 3 mm (0.08 to 0.12-inches). Heat transfer from the semi-solid aluminum to the cooler steel of the die surfaces limits the minimum section thickness. The high heat transfer rates restrict the distance that the semi-solid slurry will flow, prior to the heat loss to the steel causing the alloy to solidify and thereby stop flowing. This paper will describe techniques to produce semi-solid castings with much thinner sections.

Copper die-casting is still a relatively new casting process and the numerical formulation of this process is still in its developmental stages. A casting simulation software - ADSTEFAN was used to numerically determine the porosity in edge-gated copper rotor die-casting. The results obtained from simulation were then compared to the real die-cast copper rotors that were produced. Shot profiles are shown to be very instrumental in controlling porosity. Profiles designed to pre-fill a portion of the gate end ring at the slow shot speed prior to accelerating to the fast velocity to fill the conductor bars and ejector end ring are shown to be very effective in minimizing and controlling porosity. Since the electrical conductivity of copper is nearly 60% higher than that of aluminum, substituting copper for aluminum in the rotor would markedly increase the electrical efficiency of the motor.

High-pressure die casting is a highly productive process that yields near net-shape castings at a relatively low cost. One disadvantage of die casting, however, is residual porosity that is inherently present in the castings. Semi-solid die casting is a method that is superior to die casting as it relates to porosity but has historically been a more expensive process. This is due to the higher cost of the billet feed material and the inability to easily recycle billets and runners. Slurry-on-Demand is a new semi-solid casting process that develops the semi-solid slurry directly from the liquid, thereby eliminating the cost penalties intrinsic to the billet semi-solid process. This paper will describe the Slurry-on-Demand process in detail and present case studies comparing the casting of large components using both Slurry-on Demand and conventional high-pressure die casting. It will also provide examples of quality improvements achievable by the Slurry-on-Demand process.

A turbocharger essentially consists of a turbine and an impeller wheel connected on a common shaft. The turbocharger converts waste energy from the exhaust into compressed air, which is pushed into an engine to produce more power and torque, as well as improving the overall efficiency of the combustion process. The compression ratio for modern diesel engines can be up to 5:1, which can be only achieved using a complex impeller design and very high rotation speeds (up to 150,000 rpm for small impellers). The complex geometry and very high running speeds of impellers creates high stresses at locations such as blade roots and around the bore, and so impellers normally fail from fatigue. Therefore, it is vital to minimize defects while fabricating turbocharger impellers. Current methods for producing aluminum turbocharger impellers are plaster casting or by forging + machining. However, both of these current methods have serious drawbacks.