PhD opportunities

Influence of grain boundary pinning on recrystallized grain size homogeneity : multiscale modelling and application to nickel based superalloys used in aeronautic industry.

Thesis proposal

Area of expertiseComputational mechanics and Materials
Doctoral SchoolSFA - Sciences Fondamentales et Appliques
SupervisorM. Marc BERNACKI
Co-supervisorMme Nathalie BOZZOLO
Research unitCentre for material forming
KeywordsFE simulation, numerical and experimental metallurgy, numerical and experimental metallurgy, HPC in materials science
AbstractMINES ParisTech and co-funded by ANR and ArcelorMittal, ASCOMETAL, AUBERT & DUVAL, CEA, Framatome and SAFRAN. This Chair deals with the Development of an Innovative and Global framework for the ModelIng of MicrostrUctural evolutions involved in metal forming processes.
This Chair is a project of the DIGIMU consortium constituted by the previous cited partners along with TIMET, CONSTELLIUM and TRANSVALOR companies. During the last six decades, Smith-Zener pinning phenomenon has been widely studied and many different analytical models have been proposed in the literature. In this context, abnormal grain growth (AGG) is a versatile phenomenon and its prediction is extremely complex. AGG can be seen as a particular metallurgical configuration where few grains grow much faster than the mean grain growth rate, leading to a bimodal grain size distribution or eventually to a single population of very large grains. Recently, a new level-set (LS) numerical approach to consider inert second phase particles (SPP) in a FE framework has been proposed and used to perform 2D GG and static recrystallization (SRX) simulations for Inconel 718. Such approach seems very promising in context of AGG. Indeed, the Smith-Zener drag effect is naturally modeled by the modification of the local mean curvature when the grain boundaries pass through the particles. AGG in 2D framework, critical stored energy context and stable subsolvus configuration were also discussed thanks to this methoda. Next steps that we will consider in the proposed work will be to deal with realistic and large 3D simulations by considering all the different metallurgical mechanims which can lead to AGG. Possible evolutions of second phase particles and resulting interactions with grain interfaces in context of near-solvus static TT will be studied. Homogenization will also be considered in order to build improved mean field models to predict AGG. Moreover a large piece of the proposed work will also be dedicated to experimental investigations. Firstly, large databases capitalized by the DIGIMU industrial partners concerning microstructure evolutions of Inconel 718 during TMT will be used to discuss the full field simulations and the proposed new main field models. Secondly, in order to validate more finely the different modeled mechanims for more prospective materials, TMT and microstructural characterizations will be realized for two other nickel-based superalloys: N19 and AD730. N19 is an alloy obtained by powder metallurgy route and is therefore much more homogeneous as compared to casted alloys. It will be a good candidate to study the coupling between the SPP evolution and the grain size distribution evolution during isothermal treatments. AD730 has chemical segregations that can lead to some kind of AGG at near solvus temperature. Thus, the study will focus on near-solvus abnormal grain growth for this alloy. Moreover, the effect of a prestrain will be investigated for both alloys.
ProfileApplied mathematics, materials science.
FundingContrat de recherche
PDF document