Preparation of Super-High Strength Bimodal Aluminum Based Nanocomposite Via Mechanical Alloying and Hot Extrusion

In this paper، bimodal Aluminum based nanocomposite prepared via mechanical alloying and hot extrusion. Mechanical alloying was used to synthesize Al2024 nanostructured powder in attrition mill under argon atmosphere up to 50 h. After mixing nanostructured aluminum and unmilled aluminum powders in low energy ball mill، the resulting composite powders were shaped through hot Pressing. Finally، the hot pressed powders were hot extruded. The microstructure and fracture surface were characterized by optical microscopy (OM)، scanning electron microscopy (SEM)، X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) equipped with energy dispersive X-ray spectrometry (EDS). In order to compare the mechanical properties of hot extruded samples، tensile، compression، and hardness tests were performed. Results showed that، with an increase in unmilled aluminum percentage، ductility of composite increased but strength and hardness decreased. The mechanisms for the simultaneously improved strength and ductility involves increased dislocation activity in the coarse-grained (i. e.، unmilled powder) regions as a result of the constraint of plastic deformation in these coarse-grained regions.