Research on the Heat Dissipation Performance of Functionally Graded Aluminum Foam Fabricated via Powder Metallurgy Integrated Forming

Open‐cell aluminum foam is widely used in heat dissipation components due to its large heat transfer surface area, high thermal conductivity, and strong fluid mixing capability. The graded structure has been demonstrated to effectively balance the trade‐off between the heat transfer coefficient and pressure drop in open‐cell aluminum foam. In this study, functionally graded aluminum foam samples with varying porosity were successfully fabricated via powder metallurgy using an integrated forming process. Their convective heat transfer coefficients, pressure drops, and overall heat transfer performance were systematically investigated under different flow velocities and compared with those of uniform aluminum foam. Simultaneously, combined with numerical simulation, the internal heat transfer mechanism was studied in depth. The results indicate that the porosity gradient significantly influences the heat transfer performance of aluminum foam. Under the current experimental conditions, when the porosity gradient is 80%–75%–70%, the gradient aluminum foam achieves the highest convective heat transfer coefficient of 832 W·m −2 ·K −1 , with a corresponding pressure drop of 3605 Pa/m. An overall evaluation factor is adopted to assess the heat transfer performance; the overall evaluation factor reaches its maximum at a flow velocity of 1 m/s, which is 5.85 times higher than that of uniform aluminum foam with the same average porosity. This is because, compared to the uniform structure, the gradient structure optimizes the fluid flow path, reduces the energy required for the fluid to overcome the resistance of the solid skeleton, exhibits higher permeability and a lower friction factor, and effectively reduces pump power loss. At the same time, the gradient structure enhances internal fluid disturbance, increasing the amount of heat transferred per unit time. The synergistic effect of these two factors enables the gradient aluminum foam to achieve superior overall heat transfer performance compared to uniform aluminum foam. Furthermore, due to the axially increasing fluid velocity and higher inlet kinetic energy, the negative gradient aluminum foam achieves a higher overall flow velocity and greater capability to overcome frictional resistance, thereby exhibiting better overall heat transfer performance than its positive gradient counterpart.