Strength-toughness combination in nickel matrix composites reinforced by hybrid graphene nanoplatelets-titanium diboride

Synergistic strengthening has attracted increasing attentions for exploring advanced metal matrix composites with considerable strength-toughness. In present study, nickel (Ni) matrix composites reinforced with hybrid graphene nanoplatelets (GNPs) and titanium diboride (TiB2) particles were fabricated by a two-step 3D vibration milling strategy. Characterization results show that both the GNPs and TiB2 are homogeneously dispersed, and the TiB2 acting as the extra milling media could relieve the stacking of exfoliated GNPs. The further refined matrix grains were achieved by introducing the hybrid GNPs-TiB2, and the obtained composites demonstrated the significantly improved tensile strength of 825 MPa (74.8% higher than that of milled Ni), derived from the synergistic strengthening effects. Meanwhile, the well-maintained fracture elongation of 27.4% was acquired for GNPs-TiB2/Ni composites, exhibiting a better combination in strength and ductility compared to individual GNPs or TiB2 reinforced Ni-based composites. Furthermore, the composites with hybrid GNPs-TiB2 also revealed the high toughness modulus, which can be attributed to the improved strain hardening capacity as well as GNPs-induced bridging and pull-out effects. This work provides an effective route to fabricate and design advanced Ni matrix composites with both superior strength and toughness.