Microstructure, Thermal Transport, and Dry-Sliding Tribology of Powder-Metallurgy Al7075 Composites Reinforced With Sol-Gel-Derived ZnO-rGO Hybrid Nanoparticles

Abstract

Al7075 hybrid nanocomposites reinforced with sol-gel-derived ZnO-rGO nanoparticles were fabricated by powder metallurgy to examine whether a single hybrid architecture can simultaneously improve hardness, thermal transport, and dry-sliding behavior. ZnO-rGO hybrids containing 1-10 wt.% rGO were synthesized, blended with Al7075 at a fixed total reinforcement loading of 15 wt.%, compacted at 60 MPa, and sintered at 550 degrees C under Ar. X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy (SEM), field-emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy confirmed the retention of wurtzite ZnO and reduced graphitic carbon, uniform hybrid dispersion, and limited interfacial ZnAl2O4 formation. Relative to unreinforced PM Al7075, the best-performing hybrid increased hardness from 65 +/- 4 to 107 +/- 5 HV30 and effective thermal conductivity from 7.84 to 13.27 W m-1 K-1, while reducing the mean coefficient of friction from 0.506 to 0.231 and wear loss from 90.4 to 56.1 mg under 10 N, 50 mm s-1, and 1000 m. The improvement is attributed to a complementary hybrid mechanism in which ZnO provides load-bearing support and dispersion strengthening, whereas rGO contributes low-shear lamellar sliding, interfacial strengthening, and improved heat spreading. These results identify rGO-rich Al7075-ZnO-rGO composites as promising lightweight materials for dry-sliding components requiring enhanced durability and heat dissipation.