Simultaneously improving the strength and ductility of AZ91/GNPs composites through decorating graphene nanoplatelets with MgO
Pingbo Wang, Jun Shen, Tijun Chen, Jiqiang Ma, Qinglin Li, Shaokai Zheng
Abstract
Magnesium matrix composites (MgMCs) have always suffered low strengthening efficiency and poor ductility due to the difficulties in pursuing the well-bonded interface. Herein, graphene nanoplatelets (GNPs) were decorated with magnesium oxide nanoparticles (MgO NPs) through chemical co-precipitation and then incorporated into AZ91 alloy to fabricate MgMCs via powder thixoforging. The effect of MgO on the interface of the Mg/graphene system was investigated based on the first-principles calculations, and the result indicated that modifying GNPs with MgO NPs was helpful in improving the Mg-GNP interface bonding. The interface structural analysis revealed that the MgO NPs were firmly bonded with both GNPs and α-Mg through the distortion area bonding and semi-coherent interfacial bonding, severing as a bridge to fasten the interface bonding of composites. In addition, the MgO NPs on GNPs acted as a barrier to prevent GNPs from seriously reacting with the AZ91 alloy. As a result, the AZ91/MgO@GNPs composite was endowed with enhancements of 31% and 10% in the yield strength, and increments of 71% and 61% in elongation compared with the AZ91 alloy and AZ91/GNPs composite, respectively, exhibiting a more significant potential in optimizing the strength-toughness tradeoff compared with the AZ91/GNPs. Moreover, the possible strengthening and toughening mechanisms were also discussed in detail. This work offers a relatively novel surface modification strategy to modulate the Mg-GNP interface for a simultaneous improvement of strength and ductility.