Hot deformation behavior of a Sr-modified Al-Si-Mg alloy: Constitutive model and processing maps
(1. School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China;
2. Light Alloy Research Institute, Central South University, Changsha 410083, China;
3. State Key Laboratory of High Performance Complex Manufacturing, Central South University, Changsha 410083, China)
Abstract: Isothermal compression experiments were conducted to study the hot deformation behaviors of a Sr-modified Al-Si-Mg alloy in the temperature range of 300-420 °C and strain rate range of 0.01-10 s-1. A physically-based model was developed to accurately predict the flow stress. Meanwhile, processing maps were established to optimize hot working parameters. It is found that decreasing the strain rate or increasing the deformation temperature reduces the flow stress. The high activation energy is closely related to the pinning of dislocations from Si-containing dispersoids. Moreover, the deformed grains and the Si-containing dispersoids in the matrix are elongated perpendicular to the compression direction, and incomplete dynamic recrystallization (DRX) is discovered on the elongated boundaries in domain with peak efficiency. The flow instability is mainly attributed to the flow localization, brittle fracture of eutectic Si phase, and formation of adiabatic shear band. The optimum hot working window is 380-420 °C and 0.03-0.28 s-1.
Key words: Al-Si-Mg alloy; constitutive model; processing map; microstructure