Strengthening of aluminum piston alloy through Al2O3 nanoparticles incorporation

Aluminum alloys are widely utilized in piston manufacturing for internal combustion engines due to their high thermal conductivity, low density, and excellent machinability. However, their relatively moderate mechanical strength limits performance under severe operating conditions. In this study, the mechanical properties of an aluminum piston alloy (EN AB-47100, AlSi12Cu1) are enhanced through the incorporation of Al2O3 NPs as reinforcement. Composites are fabricated using the stir casting technique with Al2O3 NP additions of 2 wt.%, 4 wt.%, and 6 wt.%. The influence of reinforcement content on tensile strength, hardness, and impact strength is systematically investigated. The results showed that the tensile strength increased from approximately 180 MPa for the base alloy to 220 MPa and reached a maximum of 255 MPa at 4 wt.% Al2O3 NPs, followed by a decrease to 230 MPa at 6 wt.%. Similarly, hardness values increased progressively with reinforcement, achieving maximum improvement at 4 wt.% due to enhanced resistance to localized plastic deformation. The impact strength also improved from about 5.5 J for the base alloy to 7.6 J at 4 wt.% reinforcement, indicating better energy absorption capability, before decreasing at 6 wt.% due to increased brittleness. The observed improvements are attributed to effective load transfer, dislocation hindrance, Orowan strengthening, and grain refinement resulting from the uniform dispersion of Al2O3 NPs. However, excessive reinforcement (6 wt.%) led to nanoparticle agglomeration, increased porosity, and weak interfacial bonding, which negatively affected the mechanical performance. The findings indicate that 4 wt.% Al2O3 NPs is the optimal reinforcement level, providing the best combination of tensile strength, hardness, and impact resistance. These results highlight the potential of Al–Al2O3 NP composites for enhanced performance and durability in piston applications under demanding service conditions.