Quasi-continuous GNS network induced local dynamic recrystallization along interfaces in titanium MMCs under high strain rate loading

Abstract

Despite extensive research on graphene reinforced metal matrix composites (MMCs) over the past decade, the microstructure evolution of the composites still remains inexplicable, especially for dynamic loading conditions. The present work adopted a Ti–6Al–4V composite reinforced with quasi-continuous graphene nanosheets (GNSs) networks to investigate the role of reinforcement and its architecture on the mechanical response, microstructure evolution, and failure mechanism at different loading rates via Hopkinson bar system, Raman and X-ray diffraction examination, transmission electron microscope, and electron backscatter diffraction system. The results reveal that GNSs provide a significant strength improvement, owing to the formation of a quasi-continuous network comprising of GNSs and in-situ produced TiC particles. It is also found with microstructural examination that the local deformation is primarily mediated by the matrix, for which abundant local dynamic recrystallization was detected along the network-matrix interface. This may account for the reduced strain rate sensitivity and a propensity for adiabatic shear band (ASB) under impact loading for the composites. The mechanism of action of the quasi-continuous GNS network architecture is discussed in terms of the strengthening, strain rate sensitivity and ASB propensity of the composites with a quantative assessment.