Controllable bimodal structures in hypo-eutectoid Cu–Al alloy for both high strength and tensile ductility

To effectively demonstrate the dependence of ductility improvement on the scheme of introducing bimodal structure into nanostructured materials, a three-step processing was adopted in hypo-eutectoid Cu–Al alloys to obtain controllable bimodal structure of micrometer-grained pre-eutectoid phase embedded on ultrafine-grained (UFG) matrix with eutectoid composition: (1) pre-deformation heat-treatment was proposed to achieve controlled distribution of pre-eutectoid phase in the matrix with eutectoid composition, (2) both pre-eutectoid phase and eutectoid matrix were refined to submicrometer level by usage of high-pressure torsion (HPT), (3) annealed HPT-processed samples at selected temperature. All samples subjected to this novel processing route imparted a high strength, meanwhile obvious uniform plastic elongation in tensile deformation was also observed at those with bimodal structure.