Effect of Hot Extrusion Ratio on the Mechanical Properties and Microstructure of a 0.5 wt.% Graphene Nanoplatelet-Reinforced Aluminum Matrix Composite

A 0.5 wt.% graphene nanoplatelet-reinforced aluminum composite (0.5 wt.% GNPs/Al composite) was prepared by powder metallurgy and extruded at ratios of 8:1, 11:1, 17:1, 25:1 and 36:1 to study the effects of the extrusion ratio on the mechanical properties and microstructure of the composite. It is found that the composite shows the best general mechanical properties at an extrusion ratio of 17:1 tensile strength of 164.49 MPa, elongation of 21.81%, bending strength of 325.47 MPa, and a Young's modulus of 62.01 GPa. An extrusion ratio (8:1 or 11:1) that is too low results in poor grain refinement, separation of the GNP layers and ordinary properties. However, an extrusion ratio that is too large can also lead to grain growth (such as 25:1) or a reduction in GNP integrity (such as 36:1), which affects the strengthening efficiency of hot extrusion negatively.