Fabrication and strengthening mechanisms of magnesium matrix composites with bimodal microstructure induced by graphene nanoplatelets

Magnesium (Mg) matrix composites have the potential to improve energy efficiency and system performance in aerospace, automobile, mobile electronics and biomedical applications. In this work, a novel graphene nanoplatelets (GNPs) reinforced Mg matrix composites with the bimodal microstructure have been fabricated. The combination of bubbles assisted assembly method, liquid metallurgy process and hot extrusion was developed to smash the agglomeration of nanoplatelets and construct the bimodal microstructure of the Mg/GNPs composites. The theoretical calculation for strengthening mechanisms showed that the enhanced strength of the composites were mainly contributed by the grain refinement effect and the load transfer effect by GNPs. Because of the concave function relationship between the grain size and the corresponding increased yield strength, the bimodal microstructure significantly improved the strengthening efficiency of the composites, which was superior to the composites with uniform refined grains. This behavior demonstrated new possibilities for scientific and technological advantages with architecture design of composites.