Fabrication and characterization of GNPs and CNTs reinforced Al7075 matrix composites through stir casting process

In the present research, effect of graphene nanoplates (GNPs) and carbon nanotubes (CNTs) addition into the Al7075 matrix through the stir casting method on the microstructure and mechanical properties of fabricated composites was investigated. XRD results represented that by addition of reinforcements into Al7075, the dominant crystal orientation changed from a weak (002) to a strong (111). By increasing of reinforcements, the fraction of porosity increased and among the two mentioned reinforcements, addition of GNPs in to the Al7075 matrix led to create a higher fraction of porosity. Addition of reinforcements into Al7075 matrix owing to agglomeration of reinforcements and formation of porosities did not change the experimental Yield strength (YS) considerably. Theoretical calculations to determine the contributions of strengthening mechanisms in the enhancement of YS revealed that by addition of reinforcements, the grain size of matrix did not decrease, so Hall-Petch was not activated. By addition of self-lubricant GNPs and CNTs into the matrix, the wear rate values decreased and the lowest friction coefficient and the highest wear resistance belonged to Al7075/0.53 wt. % CNTs. In Al7075/GNPs, the dominant mechanisms were adhesion and delamination and a little abrasive occurred.