In-situ characterization of the sintering process in ferrous compacts through thermal diffusivity measurement

The sintering of ferrous powder compacts was studied in situ by measuring the thermal diffusivity a in a laser flash apparatus. Thermal diffusivity is a measure to characterise the heat flow through a material and depends on the contact area between the paricles and their change during sintering. It is shown that the change of a during sintering is much less pronounced than in the case of cemeted carbides which is not surprising when regarding the widely differing porosity changes. The results are however in good agreement with expectations, the only limiting parameter is the interrupted heating. Shooting a laser pulse demands isothermal conditions for the whole sample, between the pulses the sample is heated with a constant rate. Nevertheless, the trend for the thermal conductivity e calculated from a specific heat and the density is in good agreement with that found for electrical conductivity, both properties being linked through Wiedermann-Franz law, if the metallic character dominates in the sintering contacts.