Interface evolution and mechanical properties of nickel coated graphene nanoflakes/pure titanium matrix composites

The uncontrollable interface reaction has always been a difficult issue in fabricating graphene reinforced titanium matrix composites during high temperature processing. To overcome the graphene nanoflakes (GNFs) agglomeration and relieve the severe C–Ti interface reaction, electroless plating method was applied to synthesize high-quality nickel coated graphene nanoflakes (Ni-GNFs) as reinforcements in Ti matrix. In the present work, the Ni-GNFs/Ti composites were fabricated by spark plasma sintering (SPS) and subsequent heat treatment (HT). The investigations of microstructure revealed that nickel-plating layer played an important role in controlling the degree of interface reaction, and the intrinsic nanostructure of GNFs was maintained after HT at 1123 K for 15min. Feather-shaped NiTi₂ precipitation was generated when the nickel layer diffused into Ti matrix. A special crystallographic orientation relation of NiTi₂ (1¯33)//Ti (100) and NiTi₂ (51¯1¯)//Ti (1¯11) was found between NiTi₂ and Ti matrix, which accounted for the improvement of load transfer capability. The compressive tests showed that the yield strength reached to 873 MPa when the composites containing only 0.05 wt% GNFs, which was an increase of 30.1% compared to the pure titanium. This work provides a new strategy for the interface microstructure design of bulk nano-carbon/titanium composites.