Densification of potassium-doped tungsten during sintering

• Usage of thermo-optical device for in-situ measurement of shrinkage during sintering.
• Experimental data allow calibration of master sintering curve model parameters.
• Resulting model predicts density evolution regardless of heating regime.

Tungsten is traditionally sintered at very high temperatures. The master sintering curve (MSC) for densification is a functional model that describes sintering under an arbitrary time–temperature regime of a particular material during heating. The MSC for potassium-doped tungsten (W-K) has been determined by fitting experimental relative density data results versus work of sintering data with a modified sigmoid function. Five independent parameters of the fitting function are identified by minimizing error in terms of mean residual square. For measurement of relative density during sintering, we developed a non-contact high temperature dilatometer experiment using an optical method. Densification was continuously recorded at constant heating rates of 5, 10, 20, 30 and 40 °C/min. The work presented here was carried out to predict and control densification evolution of W-K during free sintering. The results demonstrate, that the MSC model of W-K describes densification independently of selected temperature regime.