Modelling Dissolution of Precipitate Phases During Homogenization of Aluminum Alloy B319

Abstract

Increasing the knowledge about the heat treatment of Aluminum alloys as light metals can be useful since these alloys are used in automotive industry, and optimizing their heat treatment processes can be beneficial economically. Aluminum B319 which is of the type Al-Si-Cu-Mg was used in this study. The result of a theoretical study of diffusion-controlled dissolution of planar, cylindrical, spherical and elliptical θ-Al2Cu precipitates are presented. Graphical relationships between the precipitate size and dissolution time were developed for a constant diffusion coefficient. The validity of various approximate solutions including: stationary interface, moving boundary using MATLAB and moving boundary using COMSOL software were considered. COMSOL was capable of two-dimensional and three-dimensional modelling. In addition, the dissolution of the Q-Al5Mg8Si6Cu2 precipitate which is a multi-component phase — that involves the diffusion of more than one component during the dissolution process — as well as the concurrent dissolution of θ-Al2Cu and Q-Al5Mg8Si6Cu2 were modelled using MATLAB. Both two and three-dimensional models were developed using COMSOL. Numerical models were validated through a series of experimental measurements using a fluidized bath furnace. The results show that the model predictions are in good agreement with the experimental results and little variations are due to the simplifications made in the model. The effect of Secondary Dendrite Arm Spacing (SDAS) on dissolution time was also examined and it was shown that the model developed was able to accurately capture these effects as well on the time required for dissolution to of these phases to occur. The model can be used as a tool to identify potential optimisation strategies for industrial solution heat treatment processes.