This is one of the projects carried out in collaboration with scientists outside the FAM group
Modelling the microstructure development during austenite decomposition using phase field theory
In this project we study the potential of both 2D and 3D phase field models to describe the kinetics of the austenite ferrite decomposition and the resulting microstructure development for plain carbon steels. For this purpose we use the Micress phase field code. The phase field model was capable of reproducing the experimental transformation kinetics, using the apparent interfacial mobility as the only adjustable parameter. Modelling in 3D was shown to lead to a more realistic description of the evolving microstructure. Finally the simulations have shown that the temperature interval of ferrite nucleation determine the width of the final ferrite grain size distribution. This project in collaboration with dr. j. Sietsma (TU Delft) and ms M.G. Mecozzi (PhD student, TUDelft) and prof. M. Militzer (UBC Canada) is expected to end 2007.
Please contact Prof. S. van der Zwaag for more information about this project.
Application of the level set method for moving boundary problems in metallurgy
While the phase field method has many attractive features for modeling solid state phase transformations, the method also has some intrinsic deficiencies. In this work we explore the use of the level set model for moving interphase problems. It is shown that the method holds several advantages over the phase field method and can describe complex morphology changes during phase transformations both effectively and accurately. The work is performed in collaboration with E. Javierre Perex (PhD student) and drs C. Vuik and F.J. Vermolen, all at the Mathematics department of the TU Delft. Ms Perez is expected to graduate on this project in 2006.
Please contact Prof. S. van der Zwaag for more information about this project.
Self Healing in Aluminium alloys as studied using positron annihilation
In a collaborative project with scientist at the Positron Centre of the TU Delft (Dr H. Schut and dr. S. Houtakangas) we study the lifetime of positrons in plastically deformed aluminium alloys as a function of the prior thermal treatment. The lifetime measurements should reveal the conditions for nanodefects closure and provide explicit proof of self healing in (underaged) aluminium alloys. The project is in the start-up phase and most of the focus is now on the experimental set-up and the data analysis.
Please contact Prof. S. van der Zwaag for more information about this project.
A micromechanical mesoscale description of the transformation behaviour of TRIP steels
In this project we develop an extended micromechanical model for the deformation behaviour of TRIP steels. In this model we incorporate the crystal plasticity of both the austenite and ferrite grains, the mutual orientation effects and the crystallography of the austenite-martensite phase transformation. The model has shown that the mechanical stability of the austenite not only depends on the properties of the retained austenite grains but on the mechanical properties and orientation of the surrounding ferrite grains as well. The model is yet to be coupled to a thermodynamic/kinetic model for microstructure-composition relations for multiphase TRIP steels. The project is being conducted in collaboration with D. Tjahjanto (PhD student) and drs A. Suiker, S.R. Turteltaub and P. Rivera., all at the faculty of Aerospace Engineering of the TU Delft.
Please contact Prof. S. van der Zwaag for more information about this project.
The nucleation conditions for solid state phase transformation
In collaboration with drs S.E. Offerman, J. Sietsma and N.H. van Dijk (TU Delft) we study the nucleation conditions for solid state transformation both experimentally and theoretically. The experimental work is centered around 3D microbeam XRD measurements in which we determine both the topology and mutual orientations of the parent austenite grains and the preferential nucleation triple junction site. In the modeling work we concentrate on the conditions for barrier free nucleation.
Please contact Prof. S. van der Zwaag for more information about this project.
Determination of the transformation conditions for individual retained austenite grains in TRIP steels
In this project we employed the 3D microbeam XRD facility at ESRF to determine the transformation conditions and behaviour of individual RA grains during stepwise cooling of a TRIP steel. The measurements yielded explicit proof that the stability of the grains depend on their volume as well as their carbon concentration. The stability conditions are being studied as a function of the steel composition and the bainitic holding conditions. The work is performed in collaboration with Dr. J. Sietsma and dr.ir. S.E. Offerman, dr. N.H. van Dijk and dr. E. Molero, (all TU Delft) .
Please contact Prof. S. van der Zwaag for more information about this project.
Microchemistry effects in the recrystallisation kinetics of aluminium alloys.
As part of the large European VIRFAB project on integrated modeling of the process-microstructure-properties relation along the entire production chain of casting, hot rolling, cold rolling and annealing, we studied the effects of microchemistry on the recrystallisation kinetics. Special attention was put on the determination of the time dependent displacement of the local interface between the recrystallised region and the parent hot deformed region. Using a special high temperature EBSD set-up we demonstrated that the interface moves in a jerky mode. The observations are supported by a model. The work will be completed in 2006. In this project we collaborate with E. Anselmina (PhD student) and dr. A. Miroux, both at the NIMR Delft.
Please contact Prof. S. van der Zwaag for more information about this project.
