Tensile deformation behavior and strengthening mechanism in graphene nanoplatelet reinforced bimodal grained aluminum nanocomposite synthesized by spark plasma sintering and hot rolling

Present research work demonstrates utilization of a unique combination of consolidation techniques, spark plasma sintering and hot rolling, to fabricate bimodal Al-graphene nanoplatelet (GNP) nanocomposite, possessing excellent amalgamation of strength and ductility. Bimodal Al-GNP nanocomposites comprised of nano crystalline and microcrystalline Al (10, 20, 30, 40, 50 wt%) with 0.5 wt% functionalized GNPs were synthesized. Rolled Al-GNP nanocomposite containing 30 wt% microcrystalline Al exhibited 54% higher yield strength than rolled microcrystalline Al-GNP and 103% higher elongation than rolled nanocrystalline Al-GNP. A theoretical calculation of yield strength of the bimodal nanocomposite was carried out considering the different strengthening mechanisms viz. load transfer mechanism, grain refinement, and coefficient of thermal expansion mismatch. The load transfer mechanism contributed maximum (75%) towards strengthening in rolled 30 wt% microcrystalline bimodal Al-GNP nanocomposite. Microcrystalline Al compact fractured in ductile mode and the nanocrystalline counterpart exhibited brittle mode of failure. On the other hand, the bimodal nanocomposite showed mixed mode of fracture, ductile in microcrystalline Al regions and brittle in nanocrystalline Al regions.