Inhomogeneous elasticity and diffusion induced recrystallization

May 13, 2010

[1] Phase-field simulations with inhomogeneous elasticity: Comparison with an atomic-scale method and application to superalloys

G Boussinot et al

We present a 2D and 3D phase-field analysis of microstructure evolution in the presence of a lattice misfit and with inhomogeneous elastic constants. The method is first critically compared with a Monte Carlo modeling at the atomic scale. We then apply the phase-field model to the Ni–Al system under external load along a cubic axis. We find that the microstructure becomes anisotropic and that the situation qualitatively differs depending on the sign of the applied stress. The microstructure evolution operates mainly by shape changes and alignments of precipitates, but also by splitting of precipitates initially elongated along directions perpendicular to the stress-induced, elastically favorable directions. The final microstructure is finally qualitatively analyzed in terms of a mean field theory in which the elastic inhomogeneity is embedded into an effective eigenstrain. This analysis leads to a simple formulation which can be used to easily predict the coherent microstructural anisotropy induced by any external loading condition.

[2] The hidden link between diffusion-induced recrystallization and ideal strength of metals

G Schmitz et al

Diffusion-induced recrystallization (DIR) is a mechanism which destabilizes thin film multilayers. New grains formed are distinguished by preferred composition levels characteristic for the diffusion couple. By evaluating these concentrations for different material combinations, it is demonstrated that a break of coherency by spontaneous relaxation is the key to understand the DIR process. Based on this, a thermo-elastic model is derived to predict whether diffusion-induced recrystallization can be expected for a given multilayer and to calculate the characteristic concentration levels.

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