Microstructure and mechanical behavior of coal-derived reduced graphene oxide reinforced AA7075 fabricated via friction stir processing

Abstract

Owing to its distinctive combination of physical and mechanical properties, coal-derived reduced graphene oxide (rGO) can be an effective and sustainable reinforcement for high strength aluminium alloys. This study explores the mechanical and metallurgical properties of friction stir processing (FSP) fabricated surface composite of AA7075 using coal-derived rGO as reinforcement. Detailed examination of reinforcement dispersion and metallurgical characteristics in the developed surface composite is carried out through optical and scanning electron microscopy (SEM). The reinforced rGO particles resulted in enhanced formation of dynamic recrystallization (DRX) grains by providing more nucleation sites as confirmed by electron back-scattered diffraction (EBSD). Moreover, the dilution of Cu-rich coarse particles and the presence of η phase finer particles in the processed zone observed through energy dispersive x-ray spectroscopy (EDS) led to a finer grain microstructure. The rGO reinforced stir zone demonstrated a significant increase of 56.97 % in microhardness value, while its Charpy impact strength increased by 200 %. The enhancement in the mechanical properties is attributed to the rGO supported grain refinement through DRX. The findings of this experimental investigation provide insights into the utilization of coal-derived rGO as reinforcement for surface composite development with an exceptional combination of mechanical and metallurgical properties.