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

Ultrafine-grained (UFG) aluminum and UFG composite containing carbon nanotubes (CNTs) are fabricated by hot-rolling the ball-milled powder, and their mechanical properties are investigated at warm temperatures ranging from 423 to 523 K. A number of voids are formed at the non-equilibrium grain boundaries in the UFG aluminum during tensile deformation at warm temperatures, resulting in poor ductility. However, the UFG composite exhibits enhanced ductility as well as superior yield stress. CNTs suppress the development of non-equilibrium grain boundaries and the formation of voids, giving rise to notably enhanced ductility at warm temperatures.