Continuous strain hardening of microstructure-dependent hot-deformed hybrid GNPs-TiB2/Ni composites

Abstract

The adoption of a synergistic strengthening strategy to explore advanced metal matrix composites(MMCs) with substantial strength and toughness has attracted increasing attention. In the present study, nickel (Ni) matrix composites reinforced with hybrid graphene nanoplatelets (GNPs)-titanium diboride (TiB₂) particles were fabricated via a 3D vibration milling strategy followed by spark plasma sintering(SPS). The results show that GNPs and TiB₂ were effectively integrated into Ni powders without noticeable aggregation. The GNPs-TiB₂/Ni composites exhibited a yield strength (YS) of 171 MPa and an ultimate compressive strength (UCS) of 293 MPa at 600 ℃, marking a substantial improvement of 128.0% and 232.9%, respectively, compared to milled Ni. The incorporation of GNPs and TiB₂ enhances dislocation storage and promotes the accumulation of geometrically necessary dislocations (GNDs). STEM-HAADF images reveal that TiB₂ particles act as a pinning agent, strengthening the resistance to dislocation motion at high temperatures. The increased GND density imparts excellent work hardening capability, which counteracts dynamic softening caused by dynamic recrystallization (DRX), leading to sustained hardening behavior in the composites.