Excellent combination of strength and ductility of Al-1.2Mn alloy with multi-scale lamellar structure

By the method of cold rolling, appropriate intermediate annealing and final annealing treatments, the multi-scale lamellar structure of ultrafine grains distributed in ribbons with coarse grains was produced in an Al-1.2Mn alloy, which displayed excellent combination of high strength and good ductility compared to coarse-grained and ultrafine-grained alloys. The high strength of the alloy with multi-scale lamellar structure is attributed to back stress strengthening associated with the formation of geometrically necessary dislocations and the good ductility results from the high strain hardening rate during plastic deformation. Loading-unloading-reloading tests were carried out to measure the back stresses of the alloys. The results show that the back stress of the specimen with multi-scale lamellar structure is much higher than that of the coarse-grained specimen.