Modeling the TDFD dissolution of Al–Fe–Mn–Si particles in an Al–4.5Zn–1Mg alloy

Abstract

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, based on the thinning, discontinuation and full dissolution (TDFD) mechanism, to predict the dissolution of the Al₁₇(Fe_3.2, Mn_0.8)Si₂ particles is described. The model is capable of predicting the volume fraction and thickness of the particles during homogenization at different temperatures and time intervals. The predicted results are in good agreement with 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.

Keywords:

• Al–4.5Zn–1Mg alloy
• modeling
• dissolution
• intermetallic compounds
• analytical methods

Acknowledgements

This research was carried out under the project number MC 4.04203 in the framework of the Research Program of the Materials Innovation Institute M2i (www.m2i.nl), the former Netherlands Institute for Metals Research. The authors acknowledge C. Kwakernaak, R.W.A. Hendrikx, N.M. van der Pers and E.R. Peekstok for assistance in performing XRD experiments and providing access to SEM.