Temperature distribution for electrically conductive and non-conductive materials during Field Assisted Sintering (FAST)

During Field Assisted Sintering Technology (FAST) the temperature differences at two different positions were investigated using two pyrometers, an internal and an external one. Two substances, an electrically conductive (tungsten carbide) and a non-conductive material (96 wt.% silicon nitride with 2 wt.% alumina and yttria) were used to monitor the temperature differences between both pyrometers during heating, sintering shrinkage and dwell time by varying die geometry and heating rate. It was shown that the temperature distribution is strongly influenced by the electrical conductivity of the material as well as by tool design and setup. The alpha–beta transformation of silicon nitride was analyzed to predict the radial temperature distribution within the sample. For comparison and for visualization a dynamical FE model including piston movement for simulating sintering shrinkage was introduced. With this, a complete time dependent FAST run could be simulated. The modeled differences in temperature distribution are in good agreement with real temperature measurements as well as phase analyses.