Planar Flow Casting and Microstructure of Aluminium Silicon Alloy

Abstract

In order to scale the planar flow casting (PFC) process to industrial levels a Python model is created. The model which is based on a combination of empirical and theoretical equations, is used to explore the limits of the process. The model is independently verified with a Comsol simulation, which is extended with solidification and heat transfer physics. The model is then used as a bases for a system and control simulation of the complete planar flow casting system. Extra elements are added, such as thermal expansion, out of roundness of the wheel, crucible and actuator mechanics, and sensor behaviour. The controllability of the system using a PID controller is presented. With this knowledge, the design requirements for the adjustment of the existing PFC machine were defined, qualitatively as well as quantitatively, for the nozzle, pressure system and gap sensor. Following this, the microstructure of the material produced by the free flow casting (FFC) process is analysed. The microstructure is measured using XRD, SEM and EDS techniques. These measurements are then compared with a model based on the Scheil equation and a kinetic phase diagram, developed for the aluminium silicon alloy. The microstructure found consisted of primary silicon particles in which a significant amount of aluminium was dissolved, as predicted by the material model. The silicon particles are dispersed within an aluminium silicon eutectic matrix with rounded needle like features. The silicon particle size is in the order of 5 μm, whilst the feature size in the eutectic is in the order of 100 nm.