Strain-rate dependent deformation mechanism of graphene-Al nanolaminated composites studied using micro-pillar compression

Uniaxial compression tests conducted at various strain rates were performed to uncover the strain-rate dependent deformation mechanism of micro-pillars fabricated from bulk nanolaminated graphene (reduced graphene oxide, RGO)-Al composites. It was found that in both RGO-Al composite and pure Al pillars, compression at high strain rates resulted in a relatively smooth stress-strain response, as opposed to the jerky deformation at low strain rates, At any given strain rate, the RGO-Al composite pillars had significantly higher strengths than their pure Al counterparts, and this reinforcing effect grew to be more pronounced with increasing strain rate. In addition, the composite pillars were characterized by considerably higher strain rate sensitivity index (m) and correspondingly lower activation volume (V*) than the pure Al pillars. These observations were interpreted by a competition between dislocation generation and annihilation, a transition in the deformation mechanism over different strain rates, and the dislocation obstruction by the inter-lamella interfaces.