Electromigration-Enhanced Densification Kinetics During Spark Plasma Sintering of Tungsten Powder

The traditional theory attributes the rapid densification of spark plasma sintering (SPS) to the thermal effect of electric current. However, the nonthermal effects of electric current are still not well understood, despite its proven significance. In this study, the mechanisms by which nonthermal effects contribute to the rapid densification of tungsten powder during SPS were investigated. Electromigration was considered as an important nonthermal effect of current, and an electromigration-enhanced creep model incorporating the contribution of temperature, pressure, and electric current on densification was constructed. The kinetics model agreed well with the experimental data and was applied to evaluate the contribution of electromigration during SPS quantitatively. Although the contribution of electric current is relatively minor compared with the temperature and pressure, it is a driving force to be reckoned with in densification.