Tensile behavior and deformation mechanisms of ultrafine-grained aluminum processed using equal-channel angular pressing

The structure and deformation behavior of ultrafine-grained aluminum processed by equal channel angular pressing through plastic flow at room temperature in a strain rate interval of 1.0×10−5–8.6×10−3 s−1 have been studied. The contribution of grain boundary sliding to the overall deformation (η) was calculated using displacement of grains relative to each other in local areas of a gage length. The strength characteristics and tendency toward necking diminish when decreasing the strain rate, while elongation up to failure and η increase. Improving the ductility at low strain rates should be related to the increase in strain rate sensitivity caused by enhancing η, reaching 45% in the local areas of the neck and totaling 72% in the local areas of uniformly elongated portion. The relatively low value of the strain rate sensitivity (m=0.08) is due to the heterogeneity of grain structure in UFG aluminum.