Multi slip activation enabled excellent low-temperature strength-ductility synergy in Al–Cu–Li alloy

Abstract

Formability is the key to restrict the widespread industrial application of Al–Cu–Li alloy. And low-temperature forming has been considered to be a promising material formation technique. This work investigates the origin of the simultaneous increase in strength and ductility that takes place in Al–Cu–Li alloys at low-temperature. We found that as the temperature decreased (ranging from 298 to 77 K), both the strengthening and ductility of Al–Cu–Li alloys with full annealing (O-state) and water quenching (W-state) increased simultaneously, producing a better strength-ductility synergy compared to room temperature. The dislocation slip is the primary deformation mechanism of two different state alloys at low-temperature and room temperature. The improved ductility at low-temperature results from the activated slip systems, promoted multisystem slip, prolonged elastic-plastic transition, and larger strain gradient, which induces the deformation to be more homogeneous. The improved strength is the result of dynamic recovery inhibition, which induces an increased dislocation density. This work indicates that Al–Cu–Li alloys have good ductility at low-temperatures and promise low-temperature applications.