Recent advances in physical metallurgy modeling at ConstelliumWednesday (06.11.2019) 14:55 - 15:15 Part of:
Recent advances in physical metallurgy modeling at Constellium
Fanny Mas, Christophe Sigli
The ability to model evolution of microstructure through process and predict its impact on final mechanical properties is a key for both process control and future product development at Constellium. This presentation will address some new developments incorporated into the existing Constellium physical metallurgy modeling platform, focusing on coupling long-range diffusion (Fick’s law) to precipitation nucleation and growth (Kampmann-Wagner formalism) in a multi-component system in order to address precipitation heterogeneities. The model relies on the Calphad approach for free energy calculation during phase transformations involving non-stoichiometric precipitates. There are several cases, for which such diffusion/precipitation coupling is needed at the scale of the grain.
The results will be illustrated on different case studies:
- Al3Zr-type dispersoids formation during homogenization in both 7xxx and AlCuLi alloys: For this case, the routine starts with a solidification simulation to obtain the gradients of all elements within the dendrite, make them evolve during homogenizing while precipitating Zr at the same time. For the case of AlCuLi alloys, potential incorporation of Li into the dispersoids has been taken into account and a para-equilibrium approach has been adopted to tackle the issue of large differences in diffusion coefficients between Zr and Li.
- The precipitation of η phase during ageing of 7xxx alloys: For this case, both intra and inter-granular precipitation are simulated. In fact, the heterogeneity of precipitation within a grain originates from grain-boundary precipitation, resulting in solute depletion in its neighborhood. In addition to precipitate characteristics at each location, the result is the width of the precipitate-free zone, which is known to be one of the feature influencing toughness.
The implications of this work for other cases of interest will be discussed.