In the recent years, the automotive industry has increased the production of small, high-power gas engines as part of several strategies to attain the new "Corporate Average Fuel Economy" (CAFE) standards, while meeting consumer demand for increased performance at the same time. This trend necessitates an improvement in the thermal and mechanical fatigue strength of the aluminium alloys used in manufacturing cylinder heads and engine blocks in these engines. In the absence of changing alloy chemistry, which potentially has important implications for downstream operations such as heat treating and machining, one feasible way to improve fatigue life is to reduce the length-scales of the microstructural constituents arising from solidification that limit fatigue resistance. This, in turn, may be accomplished by increasing the cooling rate during solidification (reducing the solidification time). Conventionally, solid chills are employed in the industry to achieve this goal. A potential tactic for improving the efficacy of these chills is to incorporate water cooling. In order to assess the effectiveness of this technique, a water-cooled chill was designed and installed in a bonded-sand engine block mould package (quarter section). Twelve experiments were conducted with a conventional solid chill and a water-cooled chill (with and without delay in water cooling). The moulds were instrumented with "Linear Variable Displacement Transducers" (LVDTs) to measure the gap formation at the casting-chill interface, and thermocouples to measure the evolution of temperature at key locations in the casting and the chill. Overall, the results show that the adoption of water-cooled chill technology, if implemented carefully, has the potential to improve the cast microstructure, therefore, increase the fatigue durability of the engine blocks.
