PhD opportunities

Effect of pre-deformation on precipitation in aluminium-based alloys: Experimental study and modelling

Thesis proposal

Area of expertiseMaterials science and engineering
Doctoral SchoolSystems Engineering, Materials, Mechanics, Energy
SupervisorM. Vladimir ESIN
Co-supervisorM. Charbel MOUSSA
Research unitCentre of materials
ContactESIN Vladimir
http://www.mat.mines-paristech.fr/Accueil/Propositions-de-theses/
Starting dateOctober 1st 2020
KeywordsMicrostructure, Pr-dformation, Metal alloys, Heat treatments
AbstractTo achieve the objectives, the Centre des Matriaux (CdM) in Evry (91) and the Centre de Mise en Forme des Matriaux (Cemef) in Sophia Antipolis (06), the two laboratories of the Mechanics of Materials department of MINES ParisTech, will contribute their expertise in their respective fields of competence. The CdM will carry out fine experimental analyses of precipitation using differential scanning calorimetry (DSC), X-ray diffraction (DRX, including in situ experiments at the synchrotron) and transmission electron microscopy (TEM) as well as modeling of precipitation kinetics using Thermo-Calc and DICTRA thermokinetic simulation tools. Cemef will carry out experimental analyses of the deformed state using Electron Backscatter Diffraction (EBSD), Electron Channel Contrast Imaging (ECCI), DRX and using the TEM available at the CdM. Numerical tools developed at Cemef will be used to quantitatively analyse the effect of dislocations through the study of their densities but also of the substructures created as a function of the thermomechanical conditions applied in order to evaluate the amount of energy stored. The final modelling of the coupled and induced effect of pre-deformation (and thus of the dislocation sub-structures) on precipitation and reciprocally that of precipitates on the dislocation sub-structures will mobilise both laboratories.

The global approach consists first of all in analysing the microstructure in order to quantify quantities affected by the mechanism studied and then to model this mechanism through the evolution of these quantities as a function of the thermomechanical conditions.
For each state, particular attention will be paid to the size distribution of precipitates as well as to the dislocation substructures analysed in TEM and SEM in order to be able to model their respective evolutions according to the thermomechanical conditions used. For the reference state (without pre-deformation), precipitation kinetics will be modelled using the KWN (Kampmann-Wagner-Numerical) method. The parameters for this model (driving force of precipitation, interface composition, mobility of chemical species) will be evaluated using thermodynamic and kinetic databases using Thermo-Calc and DICTRA software [5]. The model will be calibrated using experimental data (precipitation kinetics obtained using DSC and precipitate size distribution obtained in TEM).

The deformed state will be characterized using DRX, SEM, MET and EBSD to quantify the effect of different spatial distributions of precipitates on dislocation density, mean sub-structure size, mean sub-seam disorientation and grain boundary linear density. Similarly, the evolution of these parameters during subsequent heat treatments will be studied in order to model the evolution of the sub-structures, thus enabling the restoration and formation of new grains to be modelled.
For high temperatures causing very fast precipitation kinetics, conventional means of observation are no longer suitable. In situ experiments by X-ray diffraction at the synchrotron will be carried out (for temperatures equal to and above 250 C) to analyse the interaction between precipitation and the evolution of dislocation substructures during the restoration and formation of new grains. To this end, experimental proposals will be submitted to DESY and ESRF during the first year of this study.
Thus, the metallurgical models developed in this study will then be integrated into different numerical frameworks, in full field or medium field, relating to the evolution of microstructures and/or mechanical behaviour.
The student will spend the first 9 months at the CdM in Evry, then 18 months at the Cemef in Sophia Antipolis and the last 9 months at the CdM in Evry with regular meetings by videoconference and in person to follow the progress of the study.
ProfileTo be admitted to a doctorate, the candidate must hold a national master's degree or another diploma conferring the master's degree (engineering diploma, equivalent foreign diploma, etc.), following a course of training establishing his research aptitude.
Applicants will be selected after interview before a jury assessing their research aptitude and the adequacy of their training and knowledge with the proposed thesis subject. Strong scientific knowledge, a first research experience (internship 4 months minimum), a strong motivation for research, a good level in English will be required (minimum B2).
The application must include:
a motivation letter including the candidate's professional project
a detailed curriculum vitae mentioning studies, research internships carried out, diplomas with date obtained, professional experience, research axes envisaged
a transcript of marks from the previous course (engineer and / or master cycle)
one or more letters of recommendation ...
a certificate of English level.
for a non-French speaking student, an A2 / B1 level in French (European standard) is recommended when entering a doctorate
for students who do not hold a national research masters diploma, all documents attesting to the students qualifications in research training (research internship certificates with summary of the dissertation, recommendations, publications, etc.)
a copy of identity card or passport

The documents in pdf format must be sent to recruitment_these@mat.mines-paristech.fr no later than June 8

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FundingConcours pour un contrat doctoral