Modelling Shrinkage and Neck Evolution in Sintered Astaloy® 85 Mo Powder
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Porosity and interparticle neck size are microstructural parameters that play an important role for pressed and sintered materials. The development of powdered steel microstructure during a sinter cycle depends on the sinter time and temperature, but also on initial compact density, as well as composition. To understand the effect of these various parameters on a pre-alloyed sintered steel (Astaloy® 85 Mo), a mean-field modelling approach is selected, based on a mathematical framework describing the geometrical changes in equisized spherical particles with multiple contacts due to mass transport during sintering. Multiple fluxes are considered, drawing on relevant material constants from Thermo-Calc [1] thermodynamic database, and parametrized against experimental dimensional change data for three different sinter cycles. It is shown that changes in particle size and neck geometry due to the diffusion mechanisms active during solid-state sintering can be well described for a typical sinter cycle, and that the proposed model is well-suited for integration both with thermodynamic databases and micromechanical RVE methods. This offers a novel method of studying the effect of both powder composition and sinter cycle on mechanical properties via a coupling of thermodynamic and mechanical models.
