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Fundamental principles of spark plasma sintering of metals: part II - about the existence or non-existence of the 'spark plasma effect'

 
: Trapp, J.; Semenov, A.; Eberhardt, O.; Nöthe, M.; Wallmersperger, T.; Kieback, B.

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Powder Metallurgy 63 (2020), No.5, pp.312-328
ISSN: 0032-5899
ISSN: 1743-2901
Deutsche Forschungsgemeinschaft DFG
KI506/20-2
Deutsche Forschungsgemeinschaft DFG
WA2323/10-2
English
Journal Article, Electronic Publication
Fraunhofer IFAM ()

Abstract
The mechanisms of densification in spark plasma sintering (SPS) were investigated both analytically and numerically for a model system of two spherical metallic powder particles. From the microscopic temperature distribution, the possibility of a micro-local overheating of the particle–particle contacts was analysed for different particle sizes, contact geometries, materials, and electrical loads. It is shown that, for particles below the size of one millimetre, local overheating is below one Kelvin. Subsequently, the material transport by thermomigration, electromigration, and diffusion driven by surface curvature and external pressure was derived from microscopic field distributions obtained from analytical calculations and finite-element simulations. The results show that, while the mechanical pressure accelerates material transport by orders of magnitude, the electrical current and the temperature gradients do not. It is also shown that pulsing the current has no significant influence on the densification rate.

: http://publica.fraunhofer.de/documents/N-614881.html