Beschreibung:
<jats:title>Abstract</jats:title><jats:p>The microscopic densification mechanisms of metallic systems (TiAl, Ag‐Zn) by spark plasma sintering (<jats:styled-content style="fixed-case">SPS</jats:styled-content>) have been studied by simulations and experiments. Finite element simulations showed that, despite very high current densities at the necks between metallic powder particles (≈5 × 10<jats:sup>4</jats:sup> A/cm<jats:sup>2</jats:sup>), only very limited Joule overheating can be expected at these locations (<1°C), because of very fast heat diffusion. The microscopic plasticity mechanisms under these high electric currents have been studied by transmission electron microscopy. For this purpose, thin foils have been extracted by focused ion beam at the necks between TiAl powder particles. This is the first time, to the best of our knowledge, that microscopic plasticity mechanisms at the necks between powder particles are investigated by <jats:styled-content style="fixed-case">TEM</jats:styled-content> during densification of a metallic powder. Dislocation glide and climb mechanisms were identified, followed by recovery and recrystallization. The elementary mechanism kinetically controlling these phenomena is proposed to be bulk diffusion of Al, which activation energy (360 <jats:styled-content style="fixed-case">kJ</jats:styled-content>/mol) is close to the activation energy measured for densification (308 ± 20 <jats:styled-content style="fixed-case">kJ</jats:styled-content>/mol). Comparisons of densification kinetics by <jats:styled-content style="fixed-case">SPS</jats:styled-content> (≈60‐110 A/cm<jats:sup>2</jats:sup>) and by hot pressing (0 A/cm<jats:sup>2</jats:sup>) showed no influence of current on these mechanisms. Finally, reaction experiments in the Ag‐Zn system did not show any influence of very high currents (>1000 A/cm<jats:sup>2</jats:sup>) on diffusion kinetics. Consequently, densification by <jats:styled-content style="fixed-case">SPS</jats:styled-content> occurs by classical mechanisms not affected by the current.</jats:p>