Effect of deformation modes on continuous dynamic recrystallization of extruded AZ31 Mg alloy

Abstract

Herein, uniaxial compression experiments, with a series of true strains at different temperatures (573–673 K) and strain rates (3 ×10−3 - 3 ×10−1 s−1), are conducted on AZ31 magnesium alloy with different initial textures. The deformation modes and dynamic recrystallization (DRX) behavior are investigated using electron back-scattered diffraction /transmission electron microscopy and crystal plasticity finite element modeling (CPFEM). A unitive constitutive equation is established for different initial textures, and the activation energies of extrusion direction (ED) and transverse direction (TD) samples are found to be 134.5 kJ/mol and 138.4 kJ/mol, respectively. The microstructural investigations and CPFEM simulations are performed to identify the characteristics of DRX processing during compression and categorize according to the deformation modes originating from the difference in initial texture of alloy. Moreover, it is revealed that basal<a> slip prevails in the TD sample at all strain rates under consideration, whereas prismatic<a> slip dominates the initial deformation of the ED specimen. Consequently, more pronounced kink bands and superior compressed peak stress are observed, corresponding to the higher density of prismatic<a> slip in the ED sample than that in the TD sample. Accordingly, these kink bands along with elevated deformation energies accelerate the development of an early continuous dynamic recrystallization with a higher volume fraction and a smaller grain size of the ED sample compared to the TD specimen. The improvement in strength and ductility of the ED sample after being deformed at a strain of 1.2 is attributed to the smaller grains and the weaker texture than those of the TD specimen. For the first time, the role of prismatic slips and kink bands in the recrystallization process is discussed in detail.