Phase-Field Simulations of Coarsening Kinetics of Si Precipitates in AlSi10Mg Processed by Selective Laser Melting

AlSi10Mg processed by Selective Laser Melting (SLM) exhibits fine microstructure due to the very high cooling rate reached during the process. The microstructure consists in submicron Al cells surrounded by a tight Al-Si eutectic network. Due to the heat input accompanying the deposition of a new layer, the Si precipitates coarsen and the eutectic network loosen to form a Heat Affected Zone (HAZ) at the melt-pool boundary. During a tensile test, the rupture preferentially occurs in the HAZ by decohesion between coarse Si precipitates and the Al matrix [1]. Knowing the coarsening kinetic of the Si precipitates in the HAZ with respect to the process parameters is thus of great interest to improve the mechanical properties of AlSi10Mg SLM.

With this aim in mind, the phase-field method is a powerful technique to model microstructural evolution [2]. The method describes concentrations and phases by a set of conserved and non-conserved fields with diffuse interfaces. Microstructural evolution is predicted by solving governing equations of the fields.

We propose to study the coarsening kinetics of Si precipitates in the HAZ using phase-field simulations. In the model, the initial conditions i.e. Si precipitate size and spatial distribution as well as the Si concentration in the super-saturated Al matrix are set according to experimental observations performed by X-Ray and Scanning Electron Microscope (SEM) analysis. The thermal history in the HAZ with respect to the process parameters is obtained by a calibrated thermal finite element model. The size and the morphology of the heat affected zone observed by SEM is then compared with the ones given by the phase-field model.

[1] J. Delahaye et al., Acta Mater. 175 (2019) 160–170.
[2] I. Bellemans et al., Crit. Rev. Solid State 43 (2018) 417–454.