The enhancement of warm-temperature mechanical properties of ultrafine-grained aluminum by carbon nanotubes

► Non-equilibrium grain boundaries act as sources for void formation in UFG Al. ► Ductility of UFG Alis limited by the void formation at warm temperatures. ► CNTs suppress the development of non-equilibrium grain boundaries. ► CNTs hinder void growth during tensile deformation of aluminum. ► CNTs may provide an overallimprovement of strength and ductility of UFG Al.