Investigation on the effects of powder mixing method on mechanical properties and wear resistance of Al/graphene composites

In the present study, three different methods including ultrasonication (U), low-energy mixing (LEM), and high-energy ball milling (HEBM) were used to mix Al powders with graphene nanoplatelets (GNPs). The mixed powders were uniaxially cold-pressed and sintered to produce Al/0.5 wt% GNP composite samples. The sintered samples were characterized for their microstructure, strength, and wear resistance. The results showed that HEBM method was the most effective mixing technique to disperse GNPs within the Al matrix uniformly. However, agglomeration of GNPs in the ultrasonically processed sample impeded the successful sintering of Al/GNP compacts, leading to inferior mechanical properties. The hardness and compressive strength of the HEBM-Al/GNP composite were significantly higher than those processed by two other techniques. Wear test results showed that agglomeration of GNPs could promote extensive delamination as the main wear mechanism in the U-Al/GNP composite. However, when GNPs were uniformly dispersed within the Al matrix, the friction trace became stabilized and the average coefficient of friction was reduced. As a result, the highest wear resistance and the smoothest wear track were observed for HEBM-Al/GNP composite.