Aging behavior, microstructure and mechanical properties of graphene nanoplatelets reinforced ADC12 composites fabricated by ultrasonic assisted casting

The graphene nanoplatelets reinforced ADC12 composites (GNPs/ADC12) were successfully fabricated by ultrasonic assisted casting. The aging behavior, microstructure and mechanical properties of GNPs/ADC12 composites were investigated in this study. It was found that during aging treatment, Al2Cu precipitates preferentially nucleated at the GNPs/Al interfaces and dislocations induced by GNPs. This was mainly because the dislocations and interfaces could act as preferred nucleation sites for Al2Cu precipitates and diffusion channels for Cu element. And, the addition of GNPs could result in the finer grains, more GNPs/Al interfaces and high density dislocations, thus promoting the precipitation process of GNPs/ADC12 composites. Moreover, GNPs could improve the aging strengthening effect of the composites because of the pinning effect of GNPs on grain boundaries. As a result, the yield strength of peak aged GNPs/ADC12 composites was 245.8 MPa, which was 69.9% higher than that of ADC12 alloy. The peak aged composites were mainly strengthened by dislocation strengthening mechanism, which accounted for 62.3% in total strength contributions.