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Spark plasma sintering microscopic mechanisms of metallic systems: Experiments and simulations
Author(s) -
Trzaska Zofia,
Collard Christophe,
Durand Lise,
Couret Alain,
Chaix JeanMarc,
Fantozzi Gilbert,
Monchoux JeanPhilippe
Publication year - 2019
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.15999
Subject(s) - materials science , spark plasma sintering , activation energy , powder metallurgy , joule heating , transmission electron microscopy , kinetics , composite material , metal , sintering , metal powder , metallurgy , nanotechnology , chemistry , physics , quantum mechanics
The microscopic densification mechanisms of metallic systems (TiAl, Ag‐Zn) by spark plasma sintering ( SPS ) 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 4 A/cm 2 ), 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 TEM 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 kJ /mol) is close to the activation energy measured for densification (308 ± 20 kJ /mol). Comparisons of densification kinetics by SPS (≈60‐110 A/cm 2 ) and by hot pressing (0 A/cm 2 ) 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 2 ) on diffusion kinetics. Consequently, densification by SPS occurs by classical mechanisms not affected by the current.