Constitutive model and compaction equation for aluminum alloy powder during compaction

The deformation mechanisms in powder compaction can be described by a constitutive model, which is the cornerstone for modeling the powder compaction process by finite element simulation. Therefore, establishing a proper constitutive model is of great importance to investigate the forming rule of powder compaction as well as optimize the mold design and process parameters. The compaction behavior of 6061 aluminum alloy powder was described by the Drucker-Prager Cap (DPC) model. The model parameters and the powder densification behavior were determined and investigated by various powder compaction experiments. The modified DPC model with the determined material parameters was validated using finite element simulation method in ABAQUS with USDFLD user subroutine. The simulation results are consistent with the experiment measurements indicating that the established constitutive model can accurately describe the compaction behavior of 6061 aluminum alloy powder. Especially for the relative density exceeds 0.75, the simulation accuracy is quite high, which means that the determined model can well describe the powder behaviors at later stage of compaction process. In addition, eight representative compaction equations were employed to fit the powder die compaction experimental data and the results showed that Kawakita equation is most suitable to describe the relationship between the pressure and density for the cold die compaction process of 6061 aluminum alloy powder. Taking friction coefficient and temperature into account, a warm compaction equation of 6061 aluminum alloy powder was established. High fitting precisions of the warm compaction equation were obtained with the temperature T1 of 100°C~150°C and the friction coefficient μ of 0~0.1.