France PhD Jobs in Aerospace Project 2012/2013
Modeling of Structure and Microporosity Formation
during Solidification of Aerospace Aluminium Alloys
The Research Project
Background
Future aircraft must offer reduced environmental impact, reduced operating and maintenance cost, and more comfort for passengers. To achieve this, the weight of the airframe aircraft must be further reduced. High-performance low-density aluminum alloys combined with novel design concepts lead to up to 20% weight reductions compared to the latest generation of aircraft. The manufacturing chain leading from the feedstock to the aircraft part must be adapted to the new alloys and designs. Notably, the impact of the casting process on the final structure of the part becomes more important.
During casting the liquid metal solidifies into a solid crystalline structure. The fatigue strength of the cast material depends on the size, the morphology and the chemical
composition of the microstructures, and on the size and the distribution of microporosities. These parameters are a consequence of the solidification process. The project aims at a better control of the formation of the material structure during solidification of aluminum-lithium aerospace alloys cast by the direct-chill casting process.
The solidification in this process starts with the nucleation of microscopic solid
grains in the liquid metal. First they grow in the form of free particles floating in the
liquid. They are entrained by strong liquid flows and they sediment to form a packed
granular layer. Here the grains continue growing and finally solidify into a fully solid
structure. Near the end of solidification, microporosities can form in the structure as a
consequence of nucleation of gaseous hydrogen that was dissolved in the liquid metal.
We developed a numerical model of this multiscale (micro-macroscopic) physics, to
be able to understand the highly nonlinear phenomena and improve the process. The
model is based on CFD finite-volume modeling of the macroscopic phenomena – multiphase
fluid dynamics, heat and mass transfer – coupled with models of the microscopic
phenomena – nucleation of solid grains, solidification of the grain structure. This model
is integrated in the software SOLID, which is used by our industrial partners (Constellium,
ArcelorMittal, Ascometal, Aubert&Duval, CEA). Today SOLID is the only software
that can account for the interactions between segregation and microstructure formation
on an industrial scale.
Objective
The work will consist of modeling of (1) the multiphase flow: this involves the dynamics
of free-floating solid grains, phenomena of grain sedimentation and packing, and flow
through the porous packed layer; (2) the formation of microporosities: the phenomena
involved are the transport of dissolved hydrogen, pressure relations and the nucleation
of gaseous bubbles. The project will tightly interact with a parallel PhD project investigating
detailed microscopic aspects of grain growth. This final objective is to predict
the distribution of grain structure and microporosity in the casting. The model developments
will be integrated into the existing framework of SOLID. They will be studied and
validated by comparison to experimental analyses performed with the industrial partner
Constellium CRV. The thesis is a part of the project Principia (see below) and will interact
with the other project partners. Biannual meetings of all partners will take place.
Duration 36 months, starting date between September 1, 2011 and November 1, 2011
Scientific Supervisors Herve Combeau, Professor at Ecole des Mines de Nancy
Miha Zaloznik, Associate Scientist CNRS
Funding The project Principia (Procédés industriels de coulée innovants pour l’industrie
aéronautique) is funded by the French National Research Agency (Agènce nationale de
la recherche – ANR) through the programme MatetPro (Materials and Processes). The
project consortium consists of two industrial and three academical partners: Constellium
CRV, Saint-Gobain CREE, Institut Jean Lamour, Institute of Chemistry and Materials
Paris-Est, Laboratory of Process end Materials Engineering Ecole Centrale Paris.
Requirements for Applicants
Master’s degree in materials science, mechanical engineering, or physics
Good notions of heat & mass transfer, fluid dynamics, numerical methods
Proficiency in computer programming (Fortran 90)
Interest in numerical modeling, experience with the finite volume method appreciated
Additional Information
Work location Institut Jean Lamour, Departement SI2M – Solidification Group, Ecole
des Mines de Nancy, Parc de Saurupt, Nancy, France
Institut Jean Lamour consisting of more than 450 researchers, PhD students and technical
staff, is the largest materials science research center in France. It was created in
2009 by the fusion of five laboratories and we work in metallurgy, nanomaterials, plasma
physics, surface physicochemistry. The Department of Science and Engineering of Materials
and Metallurgy (SI2M) works mainly in metallurgical processes ranging from liquid
metal treatment over solidification to solid transformation processes; all with the
objective to control the formation of the structure of the final product. In the Solidification
Group we study the formation of the structure during solidification of aluminum
alloys, steels and titanium aluminides, by modeling and experimentation. We work in
a tight collaboration with the industry and with international academic partners on a
wide spectrum of projects, integrating industrial and fundamental problems. The SI2M
department is located at the Ecole des Mines de Nancy. We are comprised of about 90
people, thereof 35 PhD students from 11 countries.
Nancy has a population of 400 000 (metropolitan area) and is a major city in the region
of Lorraine in the east of France. It is a strong center of higher education and research,
with three universities and a total of 50 000 students. It has a flourishing student life
and offers many social, cultural and sports activities.
How to apply
Send us a short statement of your interests and your CV. For additional information
contact
Dr. Miha Zaloznik
Email: miha.zaloznik@mines.inpl-nancy.fr
Phone: +33 (0)3 83 58 41 41
Prof. Herve Combeau
Email: herve.combeau@ijl.nancy-universite.fr
Phone: +33 (0)3 83 58 42 65
IJL – Dep SI2M
Ecole des Mines de Nancy
Parc de Saurupt, CS 14234
F-54042 Nancy cedex
France
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