Graphene-reinforced metal matrix composites produced by high-pressure torsion: a review

The growing demand for lightweight and high-strength materials in the aerospace and automotive industries, as well as the need for highly conductive materials such as heat sinks, electrodes and integrated circuits, has fueled the exploration of innovative composites. Metal matrix composites (MMCs) reinforced with graphene offer a promising solution, combining the inherent properties of metals with the unique characteristics of graphene. However, the fabrication of MMCs reinforced with graphene poses several challenges such as poor wettability of graphene within the metal matrix, a non-uniform distribution of graphene and graphene clustering. Various fabrication methods have been used to address these challenges; among them, high-pressure torsion (HPT) is a promising solution due to the introduction of a fine- or even nanograined structure with well-distributed graphene within the matrix through severe shear deformation. Grain boundary strengthening, Orowan bypassing due to the presence of non-shearable graphene particles, stress transfer to the reinforcements and the inherent properties of graphene can also enhance the mechanical properties of the graphene-containing MMCs produced by HPT. On the other hand, HPT negatively affects the electrical conductivity of the metal matrices by increasing the dislocation density and the number of grain boundaries. Nevertheless, graphene can also enhance the electrical conductivity of the composite by endowing the metal matrix with its pi electrons. A current comprehensive examination of the literature provides valuable insights into the development of graphene-reinforced metal matrix composites fabricated by HPT and gives additional information on their potential applications.