抄録
In order to evaluate the strain rate dependence of the dynamic flow stress of aluminum alloys, 2017-O and -T4, high strain rate tests were performed at strain rates ranging from 1×103s -1 to 3×104s -1, and strain rate reduction tests were also conducted in the strain rate range from about 1×104s -1 to 3×104s -1, and the reduction in strain rate is 58.6%. A steep increase in the flow stress was observed for 2017-O at the strain rate of about 4 ×103s-1. For 2017-T4, the above phenomenon was observed at the strain rate of about 1 ×104s -1. A simplified model for dislocation kinetics under dynamic plastic deformation is used which can represent a transition in the rate controlling mechanism of dislocation motion from a thermally activated process to a viscous drag. It is confirmed that the steep increase in the flow stress of 2017-O and -T4 observed at the above-mentioned high strain rates is attributed to the rate dependence of the viscous drag on the dislocation motion and furthermore,the increase in the mobile dislocation density shifts the transition region, or the strain rates in which the steep increase in the flow stress becomes to appear, to the higher strain rate side.
