Constitutive modeling of the behaviour of cermet compacts during reaction sintering

This study deals with the identification of a constitutive equation describing the mechanical behaviour of a nickel ferrite based cermet during sintering. This constitutive equation considers the material as a continuum and may enable one to predict the densification behaviour of a powder under different thermal treatments and the impact of compact geometry, external loading on strain and stress generation. A classical viscous equation of the Newtonian type that includes a term describing free sintering densification has been chosen. The method used for the identification of the parameters of this equation is the one proposed Gillia et al., which is based on dilatometry measurement. It includes a stairway thermal cycle for the determination of the free sintering term and intermittent loading for estimating the viscosity. This approach has been successfully applied to nickel ferrite cermet. The model has been found to be adequate to model the densification behaviour up to 1250 °C, but experimental and theoretical efforts must be accomplished to describe the behaviour above this temperature, when the material exhibits swelling.

The densification of a nickel ferrite based cermet is described by a constitutive equation. This constitutive equation considers the material as a continuum and may enable to predict the densification behaviour of a cermet powder under different thermal treatments. This approach has been successfully applied to nickel ferrite cermet which involves precipitation-dissolution mechanisms for sintering. Simulation of the densification of the cermet during a thermal cycle with 2 °C/min rate and comparison with experimental data.Figure optionsDownload as PowerPoint slide