Metal powder pressing is an important key process in the field of powder metallurgy, and the densification process and the degree of densification are affected by factors such as powder properties, die parameters, and the pressing process. Since it is difficult to accurately calculate the number of powder particles by traditional methods, a multi-particle model combining the discrete element method (DEM) and the finite element method (FEM) is used in this study to analyze the effects of the powder stacking structure, the metal composition ratio, the pressing force, the holding time, and the friction coefficient of the inner wall of the die on the densification process. In the modeling process, each powder particle is treated as an individual and represented using the von Mises yield function and Cauchy stress. In this paper, the bi-directional compression molding process and micromechanical behavior of monometallic copper powders and copper–aluminum composite powders with the same particle size are simulated using a coupled DEM–FEM method, which remedies the lack of research in this field. First, the micromechanical behaviors of the particles during compression molding are elucidated, including shape evolution, stress distribution, and force-chain dynamics; second, the effects of aluminum content, initial packing density, and die-wall friction on densification are quantified; and then the models are validated based on empirical formulas (e.g., Hecke’s and Huang Peiyun’s equations). By sharing multi-scale simulations with parametric analysis and combining theoretical modeling with practical industrial applications, the densification mechanism of composite metal powders is dissected, which provides a sizable example for process optimization.

In this paper, the analysis method which coupled discrete element method (DEM) and finite element method (FEM) is used to simulate the double compaction of random packing of Cu and Al composite powders with multiple particle sizes. Cu and Al composite powders with varying particle size ratios from 1:2 to 1:5 were generated by DEM and then imported to MSC. Marc software (MSC.MARC2015 version) to construct FEM analysis. The effects of metal ratios, compaction pressure and size ratios on the relative density and von Mises stress of the compact were studied. The results show that the average relative density of the compact increases with the Al content, and the stress decreases. The stress in the Cu particle is particularly higher than that in the Al particle, mainly because the contact normal force of the Cu particle is nearly parallel at each contact surface. Therefore, the phenomenon of stress concentration is easier to occur within copper particles. When Al content is 30wt.%, the particle size difference enhances densification efficiency by up to 12.3%, as evidenced by an initial relative density increase from 0.7915 to 0.8047, primarily due to smaller Cu particles effectively filling interparticle voids. When the compaction pressure is fixed, the average relative density of the compact with the particle size ratio 1:5 is higher than the others, and the contact forces inside the particles significantly decrease.

In this paper, a discrete element method (DEM) coupled with a finite element method (FEM) was used to elucidate the impact of packing structures and size ratios on the cold die compaction behavior of pure copper powders. HCP structure, SC structure, and three random packing structures with different particle size ratios (1:2, 1:3, and 1:4) were generated by the DEM, and then simulated by the FEM to analyze the average relative density, von Mises stress, and force chain structures of the compact. The results show that for HCP and SC structures with a regular stacking structure, the average relative densities of the compact were higher than those of random packing structures, which were 0.9823, 0.9693, 0.9456, 0.9502, and 0.9507, respectively. Compared with their initial packing density, it could be improved by up to 21.13%. For the bigger particle in HCP and SC structures, the stress concentration was located between the adjacent layers, while in the small particles, it was located between contacted particles. During the initial compaction phase, smaller particles tend to occupy the voids between larger particles. As the pressure increases, larger particles deform plastically in a notable way to create a stabilizing force chain. This action reduces the axial stress gradient and improves radial symmetry. The transition from a contact-dominated to a body-stress-dominated state is further demonstrated by stress distribution maps and contact force vector analysis, highlighting the interaction between particle rearrangement and plasticity.