The combined effect of graphene and ceramic reinforcements on the mechanical properties, microstructural characteristics, strain-hardening behavior and Hollomon parameters of AA2024 hybrid composites was systematically investigated.
A hybrid metal matrix composite based on AA2024 reinforced with graphene (Gr), zirconium oxide (ZrO2) and boron carbide (B4C) was fabricated using the stir-casting technique. Three compositions A2024 + 0.5 wt.% Gr + 1.25 wt.% ZrO2 + 2 wt.% B4C (Sample 2), AA2024 + 1.0 wt.% Gr + 2.50 wt.% ZrO2 + 2 wt.% B4C (Sample 3) and AA2024 + 1.50 wt.% Gr + 3.75 wt.% ZrO2 + 2 wt.% B4C (Sample 4) were compared with unreinforced AA2024 (Sample 1).
Sample 4 exhibited the optimum mechanical performance, with yield strength, ultimate tensile strength, flexural strength and hardness increasing by approximately 26.8%, 18.4%, 58.4% and 33.0%, respectively. The Hollomon strength coefficient (K) increased from 733.64 ± 10.19 MPa to 866.09 ± 21.98 MPa, while the strain-hardening exponent (n) decreased from 0.1357 ± 0.00373 to 0.1147 ± 0.00406, indicating enhanced resistance to plastic deformation. However, elongation and impact strength decreased by 50.5% and 54.6%, respectively, confirming the strength–ductility trade-off. Scanning electron microscope (SEM)/Energy dispersive X-ray spectroscopy (EDS) analyses confirmed homogeneous reinforcement distribution and strong interfacial bonding, while Abaqus predictions agreed with experiments within 1–2% at higher plastic strains.
This study presents the first systematic investigation of the influence of ternary Gr–ZrO2–B4C hybrid reinforcements on the Hollomon constitutive parameters of stir-cast AA2024 composites by integrating comprehensive experimental characterization with validated Abaqus finite element modeling.
