Flow stress and dynamic recrystallization behavior of Al-9Mg-1.1Li-0.5Mn alloy during hot compression process
(1. College of Metallurgy and Material Engineering, Hunan University of Technology, Zhuzhou 412007, China;
2. CRRC Zhuzhou Electric Locomotive Co., Ltd., Zhuzhou 412004, China;
3. College of Materials Science and Engineering, Hunan University, Changsha 410082, China)
2. CRRC Zhuzhou Electric Locomotive Co., Ltd., Zhuzhou 412004, China;
3. College of Materials Science and Engineering, Hunan University, Changsha 410082, China)
Abstract: The flow stress behavior of spray-formed Al-9Mg-1.1Li-0.5Mn alloy was studied using thermal simulation tests on a Gleeble-3500 machine over deformation temperature range of 300-450 °C and strain rate of 0.01-10 s-1. The microstructural evolution of the alloy during the hot compression process was characterized by transmission electron microscopy (TEM) and electron back scatter diffractometry (EBSD). The results show that the flow stress behavior and microstructural evolution are sensitive to deformation parameters. The peak stress level, steady flow stress, dislocation density and amount of substructures of the alloy increase with decreasing deformation temperature and increasing strain rate. Conversely, the high angle grain boundary area increases, the grain boundary is in serrated shape and the dynamic recrystallization in the alloy occurs. The microstructure of the alloy is fibrous-like and the main softening mechanism is dynamic recovery during steady deformation state. The flow stress behavior can be represented by the Zener-Hollomon parameter Z in the hyperbolic sine equation with the hot deformation activation energy of 184.2538 kJ/mol. The constitutive equation and the hot processing map were established. The hot processing map exhibits that the optimum processing conditions for Al-9Mg-1.1Li-0.5Mn alloy are in deformation temperature range from 380 to 450 °C and strain rate range from 0.01 to 0.1 s-1.
Key words: Al-9Mg-1.1Li-0.5Mn alloy; flow stress; constitutive equation; processing map; dynamic recrystallization