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Temperature distribution in metallic powder particles during initial stage of field-activated sintering

: Trapp, J.; Kieback, B.


Journal of the American Ceramic Society 98 (2015), No.11, pp.3547-3552
ISSN: 0002-7820
International Conference on Sintering <7, 2014, Dresden>
Journal Article, Conference Paper
Fraunhofer IFAM, Institutsteil Pulvermetallurgie und Verbundwerkstoffe Dresden ()

The temperature distribution in copper and martensitic steel spheres has been investigated for the initial stage of field-activated sintering (FAST)/spark plasma sintering (SPS) using capacitor discharges (CD) with applied voltages from one to 15 V as model experiments. At first, the evolution of the contact resistance between the spheres has been studied. The results show the reduction in the contact resistance after discharge with increasing electrical load, yet no significant dependence on the length or number of the discharge pulses. Thereby the initial resistance is only decreased distinctly if at least a certain minimal voltage was applied. Subsequently, the melting of thin coatings of different metals on copper spheres has been studied and the occurrence of molten phase and its melting point were assigned to the corresponding discharge current. Extrapolation from the currents necessary to melt the coating layers in the CD experiments to lower values typical for FAST was used to estimate the contact overtemperature in the latter case. Resulting values for copper range from 0.05 K for normal heating with 100 K/min to 5 K for maximum current output.