Abstract
Experiments were conducted to evaluate the flow properties of an Al-3Mg-0.2Sc alloy both without and with processing using equal-channel angular pressing (ECAP). The initial grain size was ~300µm and this was reduced to ~250nm by ECAP and then increased to ~600nm by annealing at 673K for 10min. Tests were conducted to determine the mechanical properties over seven orders of magnitude of strain rate from ~10−4 to ~103s−1. The results confirm the validity of the Hall-Petch relationship in the material processed by ECAP. Shear banding occurred in the coarse-grained material during dynamic testing but in the ECAP-processed alloy there was only minor grain coarsening. There was evidence for dynamic strain ageing in both the coarse and the ultrafine-grained (UFG) alloy with a transition in flow mechanism at high temperatures from dislocation climb in the coarse-grained material to superplasticity in the UFG alloy.
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