Constitutive behavior and microstructure evolution of the as-extruded AE21 magnesium alloy during hot compression testing

• Published in: Journal of alloys and compounds 2015-02, Vol.622, p.121-129
• Main Authors: Wang, L.-X., Fang, G., Leeflang, M.A., Duszczyk, J., Zhou, J.
• Format: Article
• Language: English
• Subjects: Alloys; Compression test; Constitutive behavior; Constitutive relationships; Deformation; Flow stress; Kink band; Magnesium alloys; Magnesium base alloys; Mathematical models; Microstructure; Stress strain curves; Stress-strain relationships
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2014.10.006

•Constitutive equation of magnesium alloy AE21 for hot deformation is established.•Material processing history affects the activation energy for deformation.•Zener–Hollomon parameter is used to distinguish the shapes of flow stress curves.•Kink band plays an important role in causing a concave shape of the flow curve of AE21. Magnesium alloys containing rare earth elements possess improved corrosion resistance and mechanical properties and therefore have great potential for a wide range of applications including biomedical applications. Hot forming is meant not only for shaping but also for microstructure modification and performance enhancement. It is of great importance to define optimum forming conditions on the basis of a fundamental understanding of the response of magnesium alloys to deformation. The present study aimed at characterizing the hot deformation behavior of the as-extruded AE21 magnesium alloy by performing isothermal compression tests over a temperature range of 350–480°C and a strain rate range of 0.001–10s−1. Flow stress data obtained were intended for establishing a constitutive equation, which would be indispensable for the prediction of the response of the material to hot deformation, for example, by means of numerical simulation. The true stress–strain curves obtained from the experiments were analyzed, considering different mechanisms of microstructure evolution operating during compression testing at different stages. The Sellar and Tegart model was used to establish the constitutive equation of the alloy during the steady-state deformation. The differences in activation energy value between the present as-extruded magnesium alloy and other wrought magnesium alloys were found and attributed to materials processing history. The Zener–Hollomon parameter was used to correlate the deformation condition with the response of the material to deformation, reflected in the shape of the true stress–strain curve. Microstructure observations indicated that kink bands played an important role in determining the shape of the flow stress–strain curve of the as-extruded AE21 magnesium alloy.