Dynamic deformation behavior of ultrafine grained aluminum produced by ARB and subsequent annealing

Commercial purity aluminum (1100-Al) sheets with various grain sizes, ranging from 0.2 to 10 μm, were fabricated through accumulative roll bonding (ARB) and subsequent annealing at various temperatures. Mechanical properties of these materials were examined at various strain rates ranging from 10⁻² to 10³ s⁻¹ (from quasi-static deformation to dynamic deformation). Yield strength of the UFG specimens did not change so much when the strain rate changed. Yielding behavior of the UFG Al with grain size of 1.4 µm was characterized by yield-drop phenomenon, which appeared at higher strain rate. It was found that strain-hardening of the Al matrix was significantly enhanced at high strain rates, which was independent of the grain size. Uniform elongation increased with increasing strain rate in the specimens with the grain size larger than 1 µm, while post-uniform elongation increased with increasing strain rate in the submicrometer grain-sized specimens. Consequently, total elongation of all specimens was improved as the strain rate increased.