Microscopic mechanical properties of titanium composites containing multi-layer graphene nanofillers

• Graphenes promote significantly the indentation yield strength of the composites.
• Graphene reinforced titanium composite exhibits an improved scratch resistance.
• Graphene agglomeration leads to a decrease in mechanical properties.
• Critical length of the added graphenes in the composites was analyzed.

In this research, instrumented spherical micro-indentation/scratch tests were conducted to investigate microscopic mechanical properties of multilayer graphene (MLG) reinforced titanium based metal matrix composites (TiMMCs) synthesized using spark plasma sintering (SPS). Raman spectra and microstructure observation illustrated that MLGs survive the harsh SPS processing conditions and homogeneously distribute in Ti matrix. Instrumented indentation and scratch tests showed that mechanical properties in microscopic scale of MLG reinforced TiMMCs such as indentation yield strength and scratch resistance are significantly improved. The computed results corroborated that the critical length of most of the added MLGs satisfies the criterion of critical length of the reinforcement, and the strengthening mechanisms including enhanced dislocation density and Orowan mechanism play significant roles in the improved mechanical properties. This research is expected to facilitate a better understanding of mechanical behavior in microscopic scale of MLG reinforced metal matrix composites.

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