Hot deformation and processing maps of DC cast Al-15%Si alloy

The hot deformation behavior of Al-15%Si alloy has been studied by employing both processing maps and microstructural observations. The material of investigation was deformed by compression in the temperature range of 300-500 °C and strain rate range of 0.001-5 s−1. Processing maps were calculated to evaluate the efficiency of the hot working and recognize the instability regions of the flow behavior. The investigated alloy possesses the optimum hot-working conditions at temperature of 500 °C and strain rate of 5 s−1 corresponding to the peak efficiency of 33%, since the material undergoes dynamic recrystallization to produce a equaxied grain structure with fraction of ~53.5% of high angle boundaries. At higher temperature and lower strain rate, the material exhibited superplasticity with its maximum at temperature of 500 °C and strain rate of 0.001 s−1. Flow instability occurs at deformation temperatures ranging from 350 to 450 °C and strain rates ranging from 0.5 to 5 s−1 at strain of 0.2, and the instability domain reduces with the increasing of strain and is gradually limited to deformation temperatures ranging from 350 to 400 °C and strain rates higher than about 1 s−1.