Investigation of porosity, microstructure and mechanical properties of additively manufactured graphene reinforced AlSi10Mg composite

Abstract

Currently, additive manufacturing is a rapidly growing technique that should be explored for the development of various composites and alloys. Graphene is also simultaneously gaining considerable attention as a reinforcement material for metals due to its superior properties. In this study, a graphene/AlSi10Mg composite was developed using the powder bed fusion (PBF) technique. The effect of graphene reinforcement and laser power variation was studied on the basis of the porosity, microstructure and mechanical properties of the composite. First, graphene (0.1 and 0.2 wt.%) was mixed in AlSi10Mg powder by conducting low-energy ball milling. The resultant mixture was used for PBF at laser power values of 200, 300 and 400 W. The prepared samples were characterised by synchrotron-based X-ray computed tomography to observe their pore distribution and morphology. The observation results reveal that the energy (laser power) required for appropriate melting of the powder was increased after graphene incorporation. Electron backscattered diffraction analysis revealed grain refinement and increase in fraction of high angle grain boundaries due to progressive addition of graphene. The strain developed after graphene incorporation was also validated using X-ray diffraction analysis. The uniform distribution of graphene and its structural inherency was confirmed by Raman analysis. Moreover, transmission electron microscopy revealed a suitable graphene-matrix interface. The tensile properties were significantly influenced by the porosity induced in the samples irrespective of graphene reinforcement. However, a yield strength increase of 22 % was observed in the composite compared with the strength of unreinforced sample of equivalent density. Hardness increased progressively with the graphene content and was unaffected by variation in the laser power.