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CNRS 
Modeling of Solidification of TiAl Alloys in Hypergravity
CNRS - Université de Lorraine, Nancy
Institut Jean Lamour
Materials Science Mechanical Engineering Chemical Engineering 
Full Description:

The Solidification Group at Institut Jean Lamour is hiring a PhD student to work on the crossroads of Materials science, Thermal science and Fluid dynamics.

 

The Research Project

Background

Future aircraft must offer reduced environmental impact, reduced operating and maintenance cost, and more comfort for passengers. One of the ways to achieve this is an increase of the thrust-to-weight ratio of aircraft engines. In low-pressure turbine blades of turbofan engines, traditionally used nickel-based superalloys are being replaced by two times lighter titanium aluminides (gamma-TiAl).

The fatigue strength of metallic materials depends on the size, the morphology and the chemical composition of the crystalline microstructures. These parameters are largely determined by the solidification process during casting. Since TiAl alloys are highly reactive, centrifugal casting is used. Solidification in this process depends substantially on the strong artificial-gravity forces. To advance knowledge in this emerging technology, the ESA project Gradecet investigates the gravity dependence of solidification structures in TiAl alloys. The main questions are the transition between columnar and equiaxed microstructures, the texture evolution and the segregation of chemical elements. A series of experiments are being performed in different gravity conditions: microgravity (close to zero g) in sounding rockets, terrestrial gravity on the ground and hypergravity (up to 20 g) in ESA's large diameter centrifuge. The experiments are supported by dedicated modeling ranging from the microstructure to the casting-process scale, all converging to a multiscale representation of structure formation.

Objective

The objective of the PhD is to build and validate multiscale modeling tools that will be able to simulate the effects of gravity on the formation of microstructures and segregations in TiAl alloys at the process scale. Once established, the models will be used to simulate the Gradecet experiments and support the experimental characterizations. The PhD project will interact closely with a parallel experimental PhD project, which is funded by Snecma.

The process-scale models that will be employed are based on CFD finite-volume modeling of the macroscopic phenomena (multiphase fluid dynamics, heat and mass transfer) fully coupled with models of the microscopic phenomena (nucleation of solid grains, solidification of columnar and equiaxed grain structures). In order to provide a full picture of the physics, a combination of two complementary CFD models will be used:

- Solid®, the most sophisticated industrial-scale model of solidification today, will be adapted for the application to centrifugal casting of TiAl and will cover the full complexity of the physics in 2D.

- A new, somewhat simpler model that will cover the 3D aspects of the physics will be developed on the OpenFOAM® platform.

The thesis is a part of the Gradecet project and will interact with the activities of other project partners. Meetings of all partners are organized biannualy.

Duration

36 months, starting date between May 1 and June 30, 2015

Scientific Supervisors

Hervé Combeau, Professor at Ecole des Mines de Nancy
Miha Založnik, Associate Scientist CNRS

Funding

The PhD thesis will be funded by the European Space Agency (ESA). The project Gradecet (GRAvity DEpendence of Columnar to Equiaxed Transition in peritectic TiAl alloys) is funded by ESA, by national space agencies, and by Snecma - one of the world's leading manufacturers of aircraft and rocket engines. The project consortium consists of seven partners from five countries: Access - RWTH Aachen, German Aerospace Center (DLR), Institut Jean Lamour, Trinity College Dublin, Slovak Academy of Sciences, Snecma, and Wigner Research Center for Physics.

 

 

Requirements for Applicants

- Master's degree in mechanical engineering, materials science, or physics
- Good notions of heat & mass transfer, fluid dynamics, numerical methods
- Experience in numerical modeling (finite volume method appreciated)
- Proficiency in computer programming (Fortran 90, C++, OpenFOAM)
- Proficiency in technical report writing and presentation
- Good personal initiative, problem-solving and teamwork skills

 

 

Additional Information

Work location: Institut Jean Lamour, Campus ARTEM, 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. 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 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 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 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, including the names and contact details of two referees. For additional information contact

Dr. Miha Založnik
Email: miha.zaloznik@univ-lorraine.fr
Phone: +33 (0)3 8358 4141

Prof. Hervé Combeau
herve.combeau@univ-lorraine.fr
Phone: +33 (0)3 8358 4265

Institut Jean Lamour
Parc de Saurupt, CS 50840
F-54011 Nancy CEDEX
France
www.ijl.univ-lorraine.fr



Posted on: 03 February 2015Deadline to apply: 31 March 2015Start Date: 01 June 2015 Duration: 36 months
The Fund category is Mixed Funding and the salary is 20-25k€ annual gross
Doctoral School is Mechanics Energy Materials (EMMA) in the Lorraine Region.

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