Theoretical and experimental investigations on shear strength of Al 6061/Gr nanocomposites produced by powder metallurgy

In the present study, Al 6061/Gr nanocomposites with a nanocrystalline matrix structure containing different amounts of graphite micro-particles were synthesized via Powder Metallurgy (P/M) method through mechanical milling, cold pressing and hot extrusion. Due to the limited quantity of the produced nano-composites and impossibility of making standard tensile test specimens, a shear punch test setup was used for evaluation of the mechanical properties of these materials. The results of XRD and SEM studies revealed that Gr particles were uniformly distributed in the nanostructured Al matrix. Hardness measurements showed that increasing the volume fraction of Gr resulted in decreased hardness of Al/Gr nanocomposites. The results of shear punch tests at room temperature revealed significant higher shear yield stress and ultimate shear strength by decreasing the grain size of Al-6061. However, Gr addition deteriorated the shear strength and ductility of Al/Gr nanocomposites. These observations confirmed that the Hall-petch mechanism was the major strengthening mechanism for these nanocomposites.