Parametric studies of dynamic powder consolidation using a particle-level numerical model

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Abstract
A numerical simulation approach is used to investigate various aspects of dynamic metal powder consolidation. A two-dimensional continuum model is employed where only a few powder particles, and the interparticle voids, are considered. Consolidation is achieved by introducing large compressive stress waves in type 304 stainless-steel powder material using a high-velocity flyer plate. The effects of stress-wave amplitude on the particle deformation, consolidation rate, and temperature field are discussed based on the results of simulations using projectile impact velocities of 0.5, 1.0, and 2.0 km/s. It is demonstrated that increases in stress-wave amplitude result in higher surface temperatures leading to more extensive interparticle bonding. The 0.5 km/s impact results in full densification but is insufficient to create particle melting and bonding; the 2.0 km/s impact results in extensive interparticle melting. The effects of simple variations in the initial particle geometry are investigated by considering monosized and bimodal particle distributions and a matrix of identical hollow particles. Because each of these simulations correspond to a different initial density, the results are used to examine the effects of initial void fraction on energy deposition in the powder material during consolidation. It is shown that the average internal energy of the consolidated particles increases substantially as the initial void fraction is increased. In a final simulation, argon is placed in the regions between particles to investigate the effects of interstitial gases on the temperature field during consolidation. Shock compression of the gas results in increased surface temperatures and more extensive interparticle melting; for the materials and consolidation conditions considered, however, it is not a predominant energy deposition mechanism.