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.