AZ91 alloy nanocomposites reinforced with Mg-coated graphene: Hot-pressing sintering, heat-treatment and microstructure

Graphene has been successfully coated with the nano-Mg through organic magnesium reduction method. The nano-Mg coated graphene (GNPs) was further processed into AZ91 magnesium matrix composites through hot-pressing sintering. The effects of different solution and aging heat treatment on the microstructure evolution and interface bonding of GNPs reinforced AZ91 composites with a content of 2.5 wt% were investigated. The results show that with the increase of GNPs content, the average grain size of the composites decreases gradually, and different forms of β-Mg17Al12 precipitates in the microstructure can heterogeneously nucleate on GNPs. Compared with T4, T5 heat treatment, after T6 heat treatment, a large number of strengthening eutectic phase (β-Mg17Al12) was precipitated in the composite, which promoted the formation of a three-dimensional interlocking tight bonding structure at the GNPs-Mg interface and significantly enhanced the interface bonding strength. During the T6 heat treatment, dynamic recovery and recrystallization occurred in the composites. The area fraction of angle grain boundary increases, and the recrystallization area fraction increases from 24.49% to 75.72%. The texture intensity is obviously weakened, and the maximum texture intensity is reduced from 5.01 to 3.37.