Ultrafast severe plastic deformation in high-entropy alloy [formula omitted] via dynamic equal channel angular pressing

Abstract

An extensively investigated high-entropy alloy (HEA), Al0.1CoCrFeNi, is processed by dynamic equal channel angular pressing (D-ECAP) and subsequent annealing. Severe shear deformation and ultrahigh strain rate give rise to simultaneous activation of the {111}〈112〉 macro deformation twins and kink bands with the 〈110〉 or 〈112〉 rotation axes. Secondary kink bands are also observed in primary kink bands. With increasing annealing temperature, the deformation twins and kink bands both become less or disappear. The yield strength is increased by ∼255% solely by D-ECAP compared to the as-cast HEA. A reasonable combination of high strength and good ductility is achieved through annealing twins in recrystallized grains via annealing the D-ECAP-processed alloy at 900 °C. It is the first observation on kink bands within a face-centered cubic HEA under various loading conditions. The strengthening in these D-ECAP-processed samples before and after annealing is discussed in terms of grain boundary strengthening and dislocation strengthening.