Aging behavior, microstructure and mechanical properties of Al-Cu-Mg alloy matrix composites reinforced with carbon nanotubes

High-strength Al-Cu-Mg alloys are good matrix candidates for fabricating strong and tough Al matrix composites reinforced with carbon nanotubes (CNTs). In this study, an element mechanical alloying method was used to achieve homogeneous CNT dispersion in hard Al-Cu-Mg matrix. A comprehensive transmission electron microscopy study was applied on peak-aged CNTs/Al-Cu-Mg composites and referential Al-Cu-Mg alloy. It was found that the ex-situ CNTs increased the dislocation density and hindered the recrystallization of the Al-Cu-Mg matrix. Thus, larger local stress and strain were detected in CNTs/Al-Cu-Mg composites. The precipitation in CNTs/Al-Cu-Mg composites was accelerated, which brought extra 12 % improvement to tensile yield strength of the composite. The distribution of precipitates in CNTs/Al-Cu-Mg composites were nonuniform due to the element mechanical alloying process, which was probably beneficial to the high ductility of the CNTs/Al-Cu-Mg composite. With the synergetic strengthening effect of CNTs and fine precipitates, CNTs/Al-Cu-Mg composites exhibited well-balanced strength and ductility.