Modeling the TDFD dissolution of Al-Fe-Mn-Si particles in an Al-4.5Zn-1Mg alloy
Résumé
Dissolution of large particles in DC-cast 7xxx aluminum alloys is one of the primary objectives of the homogenization process. A mathematical model to describe and predict this complex thermodynamical and kinetical process is of great significance. In this paper, the details of a diffusion limited dissolution model developed based on the thinning, discontinuation and full dissolution (TDFD) mechanism to predict the dissolution of the Al17(Fe3.2,Mn0.8)Si2 particles are described. The model is capable of predicting the volume fraction and the thickness of the particles during homogenization at different temperatures and time intervals. The predicted results are in good agreement with the measurements using quantitative X-ray diffraction (QXRD) and quantitative field emission gun-scanning electron microscopy (QSEM). The model predictions of the supersaturation parameter, interface position, interface movement rate of the planar surfaces and the cylindrical edges, and the effect of the occurrence of discontinuities on the dissolution extent are presented.
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