Evolution of morphology in solidifying aluminium alloys

Evolution of morphology in solidifying aluminium alloys

Dijkstra, W.O.

Katgerman, L. (promotor)
Vuik, C. (promotor)

Mechanical Maritime and Materials Engineering

2007-03-13

In the thesis two different models of solidification of aluminum alloys are presented and analyzed. The first 1--D solidification model is derived from the conservation of solute, heat and mass. With numerical experiments it is shown that simulations with the Finite Difference discretization must adhere a relation similar to the Courant-Friedrichs-Lewy relation in order to get numerical stable solutions. Furthermore, it is demonstrated that depending on the chosen discretization of the interface conditions an additional singularity which can destroy stability occurs. The occurrence of this singularity is not related to the Finite Difference discretization. Singularities are also found with application of the Collocation Method. An example of a solidifying aluminum slab is successfully solved with application of the model equations and avoiding stability infringements. The possibility to apply the model in an extended simulation, i.e. especially in the second solidification model, is discussed. The second new 2--D solidification network model is used to simulate fluid flow and solidification within the mush. It is based on the assumption that the liquid parts of the mush can up to some degree be represented by a network of geometrical simplified liquid channels. Numerical simulations with this model indicate that conduction and convection of heat and solute affects directly only the permeability of a small region of the mush. Self induced effects and the formation wormholes have not been found. Finally, a detailed study of the influence of various model parameters of the network model is presented. A more detailed abstract is included within the thesis.

solidification
aluminium
permeability
mushy zone
stability
modeling

http://resolver.tudelft.nl/uuid:0c57ceb6-00b7-4434-9fee-a391208fe005

978-90-811396-1-8

Institutional Repository

doctoral thesis

(c) 2007 W.O. Dijkstra