Microstructure and hot shear deformation behavior of a fine-grained AA5083 aluminum alloy

Dual Equal Channel Lateral Extrusion (DECLE) was performed in different passes on an annealed AA5083 aluminum alloy. The microstructural evolution of the alloy was investigated using electron backscatter diffraction images and the dislocation density was determined by X-ray line profile analysis. It was found that DECLE is effective in grain refinement, and while dislocation density is almost saturated after the fourth pass of DECLE, applying the sixth pass results in more grain size reduction of annealed sample from 59.2 μm to 3.8 μm. To assess the mechanical behavior of the DECLE-processed materials, shear punch tests (SPT) at high temperatures (300–400 °C) and various strain rates (3×10−3−3×10−1s−1) were conducted. The shear stress-normalized displacement curves obtained from SPT were utilized to obtain the material constants such as the stress exponent (n) and the activation energy (Q) in the hyperbolic-sine constitutive model. The variations of n and Q were analyzed based on the microstructural features such as grain size, HAGBs fraction, dislocation density, and second phase particles fraction. The results suggest that the Q value is competitively influenced by these parameters. Accordingly, finer grain size, higher HAGBs volume fraction, lower second phase volume fraction, and smaller dislocation density result in lower Q values.