Kinetics of the β-AlFeSi to α-Al(FeMn)Si transformation in Al-Mg-Si alloys

Kinetics of the β-AlFeSi to α-Al(FeMn)Si transformation in Al-Mg-Si alloys

Kuijpers, N.C.W.

Van der Zwaag, S. (promotor)

Aerospace Engineering

2004-02-02

Among all the process steps of the production of aluminium extrusion products, the homogenisation of Al-Mg-Si aluminium billets is a very important one, since it gives significant changes in the microstructure of the alloy, leading to an improved extrudability of the material and improved properties of the final extruded product. During this homogenisation process the aluminium billets are annealed in a furnace for a few hours at a temperature of approximately 585 °C. One important microstructural change during homogenisation is the transformation of plate-like intermetallic β-Al₅FeSi particles into a string of separate coarse α-Al(FeMn)Si type of intermetallic particles. This β-to-α phase transformation considerably improves the extrusion process since the transformed α-particles in the homogenised material improve the ductility of the material and the surface quality of the extruded material. A better understanding of the β-to-α transformation kinetics is important, since this gives more insight into the effects of process parameters of the homogenisation such as temperature, homogenisation time, as-cast microstructure and chemical composition. It is the objective of this research to characterise the β-to-α transformation kinetics in Al-Mg-Si alloys (6xxx alloys) by experiments (such as optical microscopy, SEM and XRD) and to develop a physical model (FEM) that describes this transformation. Further, the research aims at gaining more insight into the behaviour of intermetallic phases during thermal processing.

aluminium
homogenisation
intermetallics
transformation
model

http://resolver.tudelft.nl/uuid:77f36876-b0d4-4a35-a9b5-7bac8c5572c5

Van Gerwen B.V.

90-77172-07-6

Institutional Repository

doctoral thesis

(c) 2004 N.C.W. Kuijpers