Abstract

The evolution of the current density and temperature distribution in the punch-die-sample set-up during field activated sintering (FAST), also known as spark plasma sintering or pulsed electric current sintering, was modelled by finite element calculations supported by in situ measured electrical and thermal input data. The thermal and electrical resistances induced by the contacts of the different constituent parts of the die-punch-sample set-up were assessed experimentally by comparing the in situ thermal and electrical response of three different graphite set-ups with increasing complexity during FAST heating, allowing for the differentiation of the influence of horizontal as well as vertical contact resistances. In the present investigation, graphite paper was used in all contacts to ensure good electrical and thermal contact conduction. The measured pulsed direct current (DC) input was converted into an equivalent constant DC current for finite element (FE) method calculations. This allowed the theoretical determination of the current and power needs in order to realize a preset temperature profile. Using the developed FE code, case studies with an electrical conductor (TiN) and an electrical insulator (ZrO2) were performed. In the case of a TiN sample, the radial temperature gradient in the sample was much larger compared to the temperature gradient in an electrically insulating ZrO2 sample. However, independent of the sample’s electrical properties, the proposed temperature measurement design allowed a very accurate temperature control since the temperature difference between the centre of the sample and the controlling pyrometer was always below 5 °C.