Reference : UPR3407-BRIBAC-003
Workplace : VILLETANEUSE
Date of publication : Thursday, September 22, 2022
Type of Contract : FTC Scientist
Contract Period : 18 months
Expected date of employment : 1 November 2022
Proportion of work : Full time
Remuneration : between 2.8 and 3.3 k€ gross per month depending on the candidate's experience
Desired level of education : PhD
Experience required : Indifferent
Ti-based alloys exhibit enhanced mechanical properties compared to most steel grades and a lower density. These alloys are therefore very attractive to reduce the weight of structures and particularly for aeronautic applications and thus to reduce also the associated carbon footprint. Among these Ti alloys, TA3V alloy is known for its high mechanical strength while remaining easy to deform at room temperature. TA3V has a two-phase (HCP) + (BCC) structure. Despite its advantages, the forming of these alloys is not totally mastered due to a very anisotropic behavior and a strong springback. Based on that observation, ANR AFoTi project (2021 - 2024) aims to improve the understanding and prediction of the microstructural evolution and behaviour of TiA3V alloys at room temperature. This project is supported by a consortium made of LPSM (UPR3407, Villetaneuse), LEM3 (UMR7239, Metz), LGF (UMR5307, Saint - Etienne).
The proposed work will be organized as follows:
- At room temperature, the network friction of the HCP structure impacts the mobility of dislocations, in particular that of screw dislocations (Peierls effect). In addition, impurities present in TA3V (such as Al, V, O) also affect the critical stress of the different slip systems. A relevant mobility law for dislocations taking into account these effects will be defined from experimental and atomistic data from the literature.
- The interactions between the different possible slip systems in the HCP structure will be studied by DDD. Simulations will take into account the previously established dislocation mobilities and elastic anisotropy.
- Massive simulations of DDD will be conducted to reproduce the plastic flow and the evolution law of dislocation densities for the single crystal of HCP crystal structure. Simulations will also be carried out on bicrystals reproducing the geometry and particular orientation of the interfaces observed in TA3V in order to study their impact on polycrystalline behavior.
- Based on these DDD results, constitutive behaviour laws will be formulated drawing on recent successes for bcc and fcc structural materials, with which the phase has similarities. The laws will be implemented in the Castem Finite Elements code in combination with the MFront behavioral law generator. They will be validated by confrontation with mesoscopic simulations and then compared with the experimental results.
With a PhD in Material science or Mechanical Engineering, the recruited candidate should have a strong experience in simulations at the atomic (MD, DFT) or mesoscopic scale (DDD would be a plus), and a solid background on defects in crystalline materials. A proven taste for simulations, scientific programming (C, python), and applied mathematics, a good level of English and an ability to work in a team are also essential.
This simulation work will be carried out at the LSPM, but a close collaboration with LEM3 and the LGF will be established from the beginning of the project, to collect the necessary experimental data, and to validate our numerical approach by confrontation with others developed at the LGF. National and international collaborations are also envisaged with our current partners on DDD (LEM, joint CNRS - ONERA unit) and National Laboratory Lawrence Livermore (Livermore, California, USA).
The candidate will have to provide, on the CNRS website a detailed CV, a cover letter, and PhD thesis reports if available; letters of recommendation can also be provided.
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