UC Davis

Cryomilled 5083 Al alloys blended with volume fractions of 15 pct, 30 pct and 50 pct unmilled 5083 Al were produced by consolidation of a mixture of cryomilled 5083 Al and unmilled 5083 Al powders. A bimodal grain size was achieved in the as-extruded alloys in which nanostructured regions had a grain size of 200 nm and coarse-grained regions had a grain size of 1 mm. Compression loading in the longitudinal direction resulted in elastic-perfectly plastic deformation behavior. As the volume fraction of coarse grains was increased, ductility increased and strength decreased. An enhanced tensile elongation associated with the occurrence of a Lüders band was observed in the bimodal alloys. Enhanced tensile ductility was attributed to the occurrence of crack bridging as well as delamination between nanostructured and coarse-grained regions during plastic deformation.