Synthesis of a novel hybrid nanocomposite of AZ31Mg-Graphene-MWCNT by multi-pass friction stir processing and evaluation of mechanical properties

Abstract

The present work is a focused study of the influence of hybridizing nano-graphene and MWCNT particulates on the microstructural and the mechanical behaviour of AZ31Mg–MWCNT-graphene hybrid composite was investigated by experimentation and its analysis. A novel hybrid nanocomposite was synthesized of AZ31Mg as base material reinforced with MWCNT and graphene nano particulates using multi-pass friction stir processing (FSP) technique. AZ31Mg plates of 6 mm thickness were drilled up to 4 mm depth with 2 mm diameter and compacted with hybrid carbonaceous reinforcements in a ratio 7:1. Multiple FSP passes were used to develop composites of AZ31Mg-MWCNT, AZ31Mg-graphene, hybrid nanocomposite AZ31Mg-MWCNT-graphene and FSPed monolithic AZ31Mg sample plates for appropriate comparison of results. The processing parameters were kept constant throughout the process for all the specimens. Microstructural characterization revealed grain refinement credited due to the uniform distribution of graphene nano-particles embedded with MWCNT. Scanning electron microscopy of AZ31Mg-MWCNT-graphene nano-hybrid composite confirmed more localized recrystallized grains and lesser tensile twin fraction, as compared to the other composites under comparison. Mechanical properties assessment specified the dominance of strength and ductility combination in the specimen of AZ31Mg-MWCNT-graphene nano-hybrid composite as compared to other composites specimens. The superior mechanical properties of the developed nano-hybrid composite attributed due to the uniform dispersion of hybridized carbonaceous nano-reinforcements and improved interfacial bonds linking the matrix and the reinforcement particles. The improvement in microhardness of the developed nano-hybrid composite is recorded as 90.6 Hv, which is much superior to other composites. The enhancements of yield strength are recorded as 32.31% and of ultimate tensile strength as 49.23%. In case of compressive strength testing, recorded improvement in 2% yield compressive strength is 50% and in case of ultimate compressive strength, it is 73.13%, whereas improvement in compressive fracture strength is noted as 8.21%, as compared to the unreinforced FSPed.