Enhanced tensile ductility through boundary structure engineering in ultrafine-grained aluminum

Commercial purity aluminum AA1050 billets with similar submicrometer grain sizes but distinctively different boundary structures were obtained by the use of different equal channel angular extrusion (ECAE) routes. Route “A” is defined as no rotation between extrusion passes, while route “C” is rotated 180° between extrusion passes. The microstructure processed by route “A” consists mainly of high-angle boundaries (HABs) while route “C” has primarily low-angle boundary (LAB) structures. Tensile tests conducted on these two microstructures at intermediate and dynamic strain rates at both 77 and 298 K were compared with the results of material tested at quasi-static strain rates. The boundary structure was found to play an important role in the mechanical properties at low temperature.