PhD thesis Niels Kuijpers




In 2004 I finished my PhD in the group of Microstructural Control of Metals (MCM) at the University of Technology in Delft, the Netherlands. This group performs research on microstructural changes during heat treatment and deformation of metals. In addition to my experimental skills, I have experience with sophisticated models of phase transformations. During my PhD I made extensive contacts with various experts in this field. I had close contacts with external industrial researchers and closely cooperate with various other academic groups internally, such as the mathematical department of the University of Delft.

In 2008 I started the company MATinspired. This company performs R&D on various types of materials for customers. Also I give causes courses in the field of material science, such as metallography and metallurgy.

My PhD subject

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

During homogenisation of Al-Mg-Si extrusion aluminium alloys, plate-like metastable monoclinic β-AlFeSi intermetallics transform to smaller and rounded cubic α-Al(FeMn)Si type of intermetallics. The a -particles give better extrusion properties to the aluminium as compared to the coarse β-particles, and therefore the solid state β to α transformation process is favorable. To analyse the nature of this phase transformation, its process was investigated by a number of different experimental techniques including Optical Microscopy, SEM, TEM, EDS and x-ray diffraction on extracted particles. A Laser Scanning Confocal Microscope (LSCM) was used to investigate deep-etched samples and to localise the α-nuclei on the β-plates. Also computational 3D reconstructions of series of 2D micrographs were analysed to study the morphology changes of the intermetallics during the homogenisation. A Finite Element Model (FEM) of the physical mechanism of the β to α transformation was made which describes the growth of a particles on the β plates. As a basis of this FEM model, thermodynamical data were used, as extracted from a thermodynamical data base (ThermoCalc). In the model the influence of different parameters on the homogenisation rate, such as temperature, alloy content, and morphology of the intermetallics, was successfully implemented.

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Publications, posters and reports:

some publications:

N.C.W. Kuijpers, F.J. Vermolen, C. Vuik, P.T.G. Koenis, K.E. Nilsen, S van der Zwaag. The dependence of the β-AlFeSi to α-Al(FeMn)Si transformation kinetics in Al-Mg-Si alloys on the alloying elements. Mat. Sci. Eng. A 394 (2005) 9-19. download

N.C.W. Kuijpers, F.J. Vermolen, K. Vuik, S van der Zwaag. A Model of the β-AlFeSi to α-Al(FeMn)Si Transformation in Al-Mg-Si Alloys, Mater. Trans. 44 (2003) 1448-1456. download

N.C.W. Kuijpers, J.Tirel, D.N. Hanlon, S. van der Zwaag. Quantification of the evolution of the 3D intermetallic structure in a 6005A aluminium alloy during a homogenisation treatment, Mater. Char. 48 (2002) 379-392. (This article has been awarded for the Buehler Merit Paper Award) download

J. van de Langkruis, N.C.W. Kuijpers, W.H. Kool, F. J. Vermolen, S van der Zwaag. Modelling Mg2Si dissolution in an AA6063 alloy during preheating to the extrusion temperature. Conference: ET 2000: Seventh International Aluminum Extrusion Technology Seminar. U.S.A, Chicago, Aluminum Extruders Council, vol 1, pp. 119-124. download

N.C.W. Kuijpers, W.H. Kool and S. van der Zwaag. DSC study on Mg-Si phases in as cast AA6xxx. Mater. Sci. Forum 396-402 (2002) 675-680. download

some posters:

N.C.W. Kuijpers, I. Todd, S. van der Zwaag. Phase transformation of beta-AlFeSi to alpha-Al(FeMn)Si phases during homogenisation of 6xxx Al alloys. PPM, Materials conference, 22-23 May 2000, Veldhoven, The Netherlands. download

N.C.W. Kuijpers, I.Todd, S. van der Zwaag. Phase transformation of second phase intermetallics in AA 6xxx during homogenization, NIMR conference, Noordwijkerhout, The Netherlands, December 6 and 7, 1999. download

N.C.W. Kuijpers, W. van Til, J. van de Langkruis, C. Vuik, S. van der Zwaag. Modelling Mg2Si Dissolution in 6063 Aluminium Alloy During Preheating to the Extrusion Temperature, FOM-meeting in Veldhoven, December 21 and 22, 1999. download

some reports:

N.C.W. Kuijpers. Literature review: Intermetallic phase transformations during homogenisation of 6xxx Al alloys, a literature review. Delft, Internal report NIMR, 2000. download

Graduation report:

I graduated in the field of Technical Physics at the University of Technology of Eindhoven, The Netherlands, in the group of Magnetism and Nano Structures.

N.C.W. Kuijpers. TU-graduation thesis at the group of Physics of Nanostructures at the University of Technology Eindhoven: Title: Characterisation of nonmagnetic and ferromagnetic tunnel junctions, 1998. download