Deformation behavior of bimodal nanostructured 5083 Al alloys

Cryomilled 5083 At alloys blended with volume fractions of 15, 30, and 50 pct unmilled 5083 At were produced by consolidation of a mixture of cryomilled 5083 At and Unmilled 5083 A] 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 I mu m. Compression loading in the longitudinal direction resulted in elastic-perfectly plastic deformation behavior. An enhanced tensile elongation associated with the occurrence of a Luders band was observed in the bimodal alloys. As the volume fraction of coarse grains was increased, tensile ductility increased and strength decreased. Enhanced tensile ductility was attributed to the occurrence of crack bridging as well as delamination between nanostructured and coarse-grained regions during plastic deformation.close10610

Mechanical properties of an ultrafine-grained Al-7.5 pct Mg alloy

In the present study, the relationships between the structure and properties of a cryomilled Al-7.5 pct Mg alloy were investigated. The microstructure of the cryomilled Al-7.5 pct Mg alloy consisted of equiaxed grains with an approximate size of 300 nm. Thermal treatment had only a minor effect on microstructure, as evidenced by X-ray diffraction (XRD) and transmission electron microscopy (TEM) results. The tensile behavior was characterized by high strength, high ductility, and low-strain-hardening. The tensile deformation was relatively uniform, with limited necking deformation, and fracture surfaces were characterized by microdimples. The variation of strain rates from 4 (.) 10(-4) to 4 (.) 10(-2) s(-1) had an insignificant effect on tensile behavior. Comparison of compressive and tensile behavior revealed similar moduli and yield strengths, although the postyield behavior was markedly asymmetric. The present results indicate that grain-size effects, solid-solution strengthening, Orowan strengthening, and dislocation strengthening contribute significantly to the properties of a cryomilled Al-7.5 pct Mg alloy.close9710