| Abstract: |
It is the surface integrity the total of surface roughness, microhardness, residual stress, and wear resistance that largely controls the in-service performance of finished aluminum aerospace components rather than any single response as previously considered in isolation. This study is a comparison of surface integrity of three commercial aluminum alloys when roller burnished with five nanofluid blends. These include: four binary formulations (Al₂O₃–CuO [75:25(c); 25:75(wt.%)], Al₂O₃–graphene [60:40(c); 40:60(wt.%)], CuO–MWCNT [50:50(c); 50:50(wt.%)], TiO₂–SiO₂ [60:40(c); 40:60(wt.%)] ) and one ternary formulation (Al₂O₃–CuO–graphene [50:30:20(c); 50:30:20(wt.%)] ) Denses, 2021. Surface-integrity components including arithmetic surface roughness (Rₐ), Vickers microhardness (HV), residual compressive stress measured by X-ray diffraction (σᵣ) and pin-on-disc wear loss were measured on the Al6061-T6, Al7075-T6 and Al2024-T3 workpieces and aggregated into a composite Surface Integrity Index (SII) via equal weighting. The best SII of 0.91 on Al7075-T6 was obtained from the ternary Al₂O₃–CuO–graphene blend, which represented a 15.2 % improvement over the best binary blend (Al₂O₃–graphene, SII = 0.79) and was nearly six times larger than the dry-burnishing baseline (SII = 0.15). The ternary benefit stems from the in-situ activation of three synergistic tribological mechanisms provided by hard γ-Al₂O₃ particles in micro abrasion, CuO carriers for thermal regulation, and graphene nanoplatelets for friction-reducing tribofilm construction. Results showed strain-hardening depths of ~0.4 mm under all the hybrid blends, with the corresponding maximum microhardness (165 HV) and the most significant absolute residual compressive stress (−432 MPa) produced by the ternary blend and confirmed by subsurface microhardness profiles. These results define the role of the new ternary Al₂O₃–CuO–graphene formulation as a truly multi-mechanism surface-integrity optimizer for the finish-burni |
