Influence of Cooling Rate on the Structure and Damping Properties of the AlSi6Cu4 Alloy

The investigated alloy was cast as a shaft into seven casting molds. Casting molds made of different materials were characterized by different abilities to conduct heat from the sample. This property significantly influenced the cooling rate of the sample casting from the AlSi6Cu4 alloy. The highest cooling rate was achieved in a steel mold at 25°C and the lowest in a mold made of insulating mass. Different cooling rates significantly influenced the structure of the alloy. Different grain sizes were obtained and the morphology of the microstructure components changed. At the highest cooling rate of 16.63 K·s−1, a grain with an average size of 0.58 mm was obtained. However, in the mold with the lowest cooling rate of 0.36 K·s−1, the average grain size was 3.76 mm. Changes in the structure of the alloy also influenced its damping properties. The tested values f the vibration damping coefficient α indicated that the AlSi6Cu4 alloy cooling with the highest cooling rate has the highest value of damping coefficient. This is influenced by the grain size and shape of the silicon precipitates. The refinement structure and fragmented components effectively disperse the vibration wave in the structure of the casting alloy.