The effect of thermomechanical parameters on the eutectic silicon characteristics in a non-modified cast A356 aluminum alloy

The influence of hot working parameters on the microstructural evolution of cast A356 aluminum alloy has been studied emphasizing the changes in eutectic phase morphology. Toward this end, a set of isothermal compression tests were conducted in the temperature range of 400–540 °C. The results indicate that the eutectic Si platelets are fragmented, spheroidized and also evenly distributed in the matrix as a result of applying proper thermomechanical cycles. The mechanical fragmentation and thermal disintegration play a prominent role in Si particles breaking up under the different deformation conditions, whereas the average particle size is decreased with decreasing the temperature and increasing the strain rate. The lowest shape factor and aspect ratio are also achieved for the specimens deformed at higher temperatures and lower strain rates. The current work also explores the high temperature flow behavior of cast A356 alloy to address the dominant restoration processes taken place at different thermomechanical conditions.

► Various thermomechanical cycles were performed on non-modified cast A356 alloy. ► Si platelets were fragmented, spheriodized and evenly distributed in the matrix. ► Mechanical fragmentation and thermal disintegration contribute to break-up of the Si particles. ► Higher degrees of spheroidization at higher temperatures and lower strain rates. ► The greater the strain rate and the lower the temperature, the higher the flow stress level.