Influence of hybrid graphene–ceramic reinforcements on Hollomon parameters and mechanical behavior of AA2024 composites

Abstract

Purpose 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. Design/methodology/approach 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). Findings 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. Originality/value 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.