The effect of strain rate on tensile behavior and deformation mechanisms of ultrafine-grained aluminum

Abstract

The effect of strain rate on strength, ductility and uniformity of deformation 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 to 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 probably due to the heterogeneity of grain structure in UFG aluminum. © Published under licence by IOP Publishing Ltd.