Pressure-driven optimization of nHA/rfGO-reinforced Mg alloys: Microstructural, mechanical, corrosion, and biological performance of biodegradable orthopedic scaffolds

Magnesium-based alloys reinforced with bioactive phases offer a promising route for developing biodegradable orthopedic scaffolds due to their combined biocompatibility, mechanical integrity, and osteogenic potential. In this study, porous scaffolds were fabricated from a Mg–4Zn–2Sn–0.3Mn alloy incorporating nano-hydroxyapatite (nHA) and reduced functionalized graphene oxide (rfGO). Using powder metallurgy and a space-holder technique, the influence of compaction pressure (125, 150, and 175 MPa) on scaffold microstructure, mechanical performance, corrosion behavior, and biological response was systematically evaluated. nHA and rfGO were synthesized via sol–gel and chemical reduction routes, and composite powders were ball-milled, mixed with 35 vol% carbamide (300–400 µm), compacted, and sintered at 540°C. Phase composition and morphology were characterized by XRD and FESEM, while pore architecture was assessed through FESEM, Archimedes, and BET analyses. The scaffolds exhibited hierarchical porosity spanning macro-, micro-, and nanoscale pores. Increasing compaction pressure decreased total porosity (28.5→25.5%) and produced more uniform, quasi-spherical pores. Mechanical testing revealed improved elastic modulus (0.85→1.12GPa) and yield strength (21.22→30.34MPa) at higher pressures, accompanied by enhanced energy absorption. Electrochemical analysis in simulated body fluid showed increased impedance (1.588→2.097kΩ·cm²) and larger EIS semicircles with rising pressure, indicating improved corrosion resistance. Biological assays (MTT, calcein-AM, ALP) demonstrated pressure-dependent cellular behavior, with the 125 MPa scaffold supporting the highest viability and osteogenic activity. These findings highlight the tunability of nHA/rfGO-reinforced Mg-based scaffolds and underscore the balance between mechanical performance and bioactivity required for biodegradable load-bearing implant applications.