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Reference : UMR5307-ROMQUE-001
Workplace : ST ETIENNE
Date of publication : Wednesday, September 1, 2021
Type of Contract : FTC Scientist
Contract Period : 18 months
Expected date of employment : 1 November 2021
Proportion of work : Full time
Remuneration : about 2700 € gross monthly salary
Desired level of education : PhD
Experience required : Indifferent
Titanium alloys show higher mechanical properties than most steels for a density 2 times lower, which makes them interesting for structure weight reduction in variaous applications (aeronautics, sport, ...). Among Ti alloys, Ti3Al2.5V is known for its high mechanical strength while being relatively prone to shaping operations at room temperature. Despite these advantages, shaping operations of these alloys are not entirely satisfying and generally results in a highly anisotropic macroscopic behavior and a strong elastic return. In the context of the AFoTi ANR project (2021–2024), also involving the LEM3 (UMR7239, Metz, France) and LPSM (UPR3407, Villetaneuse, France), the LGF (UMR5307, Saint-Étienne, France) is hiring a postdoc whose general mission is to develop a proper numerical modelling of the Ti3AlV2.5 alloy (morphology, texture, orientation relationships, etc.) and of the mechanical behavior of the different phases, and to simulate and analyze the (large) deformation of the material, both at local (grain-level) and global scales et (constitutive low, formability limit curves).
TiAl3V2.5 presents a relatively complex heterogeneous microstructure, which strongly depends on the processing steps and whose properties are naturally very important for the macroscopic mechanical behavior of the material. As a complete experimental investigation of these phenomena would be very complex and costly, we propose to quantify them via a numerical representation of the microstructures and the simulation of their deformations by the crystal plasticity finite element method. Realistic microstructures will be generated with Neper (https://neper.info) and simulations will be performed with FEPX (https://fepx.info), these 2 software packages being developed jointly by LGF and the University of Alabama (USA) since several years. The same tools have been successfully used for a study of TiAl6V4.
The proposed postdoc work will include the following steps:
- Study of the properties of the experimental microstructures and generation of corresponding numerical microstructures using the Neper software package (experimental work carried out by other members of the project, at LEM3);
- Determination of the (phenomenological) behavior law of the crystal (HCP and CC) from the literature, by inverse method, or via the dynamics of dislocations (work carried out by other members of the project, at the LSPM);
- Simulation of the deformation of the material bycrystal plasticity finite elements thanks to the FEPX software package;
- Systematic study of the deformation of the material: global behavior and local mechanisms of deformation (interaction between phases, etc.);
- Optimization of the microstructures with respect to the mechanical properties sought.
Holder of a PhD in the field of materials and/or mechanics, the recruited PhD should have skills in numerical simulation of polycrystalline materials behavior and like software development. Knowledge of titanium alloys and/or Fortran language is required. A good level of English and an ability to work in a team are also required. The candidate should provide an extensive CV, a letter of motivation and the reports of thesis referees; letters of recommendation can also be added.
This mainly numerical work will be carried out at LGF, but also in collaboration with the LEM3 to have experimental data and with the LSPM for the dialogue with the dynamics of dislocations. Collaborations are also foreseen with our current partners in the development of Neper and FEPX, mainly the University of Alabama (USA). This postdoc will be supervised at LGF by R. Quey.
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