Functionally gradient AA7075- Al2O3 composites fabrication via deformation-driven metallurgy process

This study investigates tablehe microstructural evolution and mechanical performance of functionally graded AA7075-Al₂O₃ composites processed via the deformation driven metallurgy (DDM) technique. Microstructural analysis reveals a systematic grain refinement with increasing Al₂O₃ content, where the average grain size decreases from 10.2 ± 0.8 µm at 0 wt.% Al₂O₃ to 3.1 ± 0.6 µm at 32 wt.% Al₂O₃. This refinement is attributed to dynamic recrystallization (DRX) and particle-stimulated nucleation (PSN), facilitated by Al₂O₃ particles acting as nucleation sites. Mechanical testing demonstrates significant improvements in hardness and strength. Hardness values increase from 123.6 ± 3.4 HV₀.₁ in the unreinforced sample to 313.7 ± 8.2 HV₀.₁ at 32 wt.% Al₂O₃, while ultimate tensile strength (UTS) rises from 526.4 ± 12.5 MPa to 740.8 ± 10.1 MPa. However, this enhancement comes at the cost of ductility, with elongation decreasing from 12.7 ± 1.2 % to 4.6 ± 1.7 %. Fractographic analysis reveals a transition from ductile to brittle fracture with increasing reinforcement, driven by particle-induced stress concentrations. Tribological assessment shows superior wear resistance with higher Al₂O₃ content. The friction coefficient and wear rate decrease to 0.33 ± 0.03 and 3.8 ± 0.2 µg/m, respectively, at 32 wt.% Al₂O₃.