Understanding the Manufacturing Process of Foamed Copper

Metal foams (porous metals) exhibit excellent properties in terms of energy absorption, electrical conductivity, and thermal conductivity, and are widely used in crash-absorbing components, battery electrodes, and heat exchangers. Currently, metal foams are typically manufactured through electroplating, casting, or powder metallurgy.
Among existing production processes, foamed aluminum and foamed Nickel have achieved industrial-scale application. However, due to the complexity of traditional preparation methods, foamed metals remain costly, and the pore structures produced by current processes are often suboptimal and difficult to control. Consequently, foamed metals are currently primarily used in critical high-end sectors such as the military and aerospace industries. In response to practical needs, the Advanced Forming Team has proposed a process utilizing metal powder sintering technology that allows for the flexible production of eitherclosed-cell or open-cell copper foams. This process also facilitates the convenient fabrication of copper foams with gradient porosity.
High-purity copper powder and CaCl₂ particles were used as raw materials for high-temperature sintering. Through a combination of theoretical analysis, finite element numerical simulation, and experimental research, the sintering process parameters for foamed copper were investigated, and the preparation processes for both closed-cell and open-cell foamed copper were established. Taking closed-cell foamed copper as an example, the preparation process is shown in the figure below.

The closed-cell and open-cell foamed copper specimens prepared in this study were characterized in terms of microstructure, composition, microhardness, mechanical properties, flow resistance, and filtration performance. The study successfully produced foamed copper specimens with controllable pore morphology and porosity, as well as excellent structural and functional characteristics.
As shown in the metallographic micrograph of the closed-cell foam copper pore walls below, the pore wall structure is relatively smooth and intact, with no obvious defects observed within the pore walls. This indicates that during the loose-packing sintering process involving the mixture of closed-cell foam copper samples and pore-forming foam particles, the decomposition of the foam particles at high temperatures did not cause the collapse or tearing of the pore structure, nor did the pore structure undergo significant deformation due to the volume shrinkage of the sintered body. The metallographic photographs of the closed-cell foam copper matrix metal reveal only a few voids within the matrix. The grain boundaries are distinct, and the grain shapes are nearly spherical, indicating that the matrix metal exhibits good fluidity and possesses excellent compressive properties. The SEM images of the closed-cell foam copper matrix metal show that the sintering of the powder was thorough, with no free powder particles present, indicating a high degree of densification.

The above results demonstrate that the foam copper preparation process proposed in this study is highly feasible and produces reliable final products.
The compression stress-strain curve of the copper foam exhibits a plateau; it is precisely this plateau that confers the closed-cell foam metal with its unique energy-absorption properties. The height of the plateau determines the energy absorption capacity of the closed-cell copper foam, while its width determines the energy absorption efficiency. As shown in the figure, the prepared closed-cell copper foam demonstrates excellent energy-absorption and load-bearing performance.