The Effect of a Composite Nanostructure on the Mechanical Properties of a Novel Al-Cu-Mn Alloy through Multipass Cold Rolling and Aging

An effective approach composed of solution treatment, multipass cold rolling and aging was developed to improve the strength and ductility of novel Al-Cu-Mn alloys. This approach increased the yield strength by 214 MPa over that of the conventional peak-aged samples while maintaining a good elongation of 8.7%. The microstructure evolution was examined by confocal laser scanning microscopy (CLSM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). During postaging, deformed structures underwent a considerable decrease in dislocation density and typical dislocation network structures were formed. At the same time, highly dispersed nanoprecipitates and extensive ultrafine grains and nanograins were generated. These nanoprecipitations enabled effective dislocation pinning and accumulation during tension deformation. Therefore, composite nanostructures containing ultrafine grains, nanograins, dislocation network structures and nanoprecipitates were responsible for the simultaneous increases in strength and ductility. This paper provides a new understanding of designing composite nanostructure materials for achieving high strength and good ductility that is expected to be used for other age-hardenable alloys and steels.