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Reference : UMR5510-PIEGES-001
Workplace : VILLEURBANNE
Date of publication : Monday, March 29, 2021
Scientific Responsible name : Pierre-Antoine Geslin
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
High entropy alloys (HEA) are a new class of materials that are attracting increasing attention and are considered as the alloys of tomorrow because of their superior mechanical properties. In contrast with conventional alloys composed mainly of one element, HEA are composed of multiple elements in comparable proportion. In particular, refractory HEA of body centered cubic structure such as Ta25Nb25Mo25W25 keep an outstanding high yield strength at high temperature and are thought as potential replacement of Ni-base superalloys for aerospace and nuclear applications. However, impurities such as oxygen and carbon atoms that occupy interstitial sites of these alloys lead to an increase of the yield strength but also to a drop of ductility. The evolution of these mechanical properties with the concentration of interstitial elements is therefore an important question to clarify before using these alloys in industrial applications.
In this PhD project, we propose to investigate interactions between dislocations (carriers of plastic deformation) and solutes with a multi-scale numerical approach. First, the PhD candidate will study the behavior of dislocations (edge and screw) in a HEA using molecular dynamics simulations that allow to account for the details of atomic interactions. Molecular dynamics will also alloy to clarify the role of interstitial solutes on the dislocation behavior. However, atomistic method remains limited to small length and time scales that are not representative of experimental conditions. Therefore, the second step of this project will focus on the development of an elastic approach where the dislocation is represented as an elastic line interacting with a stress field emerging from solutes. This continuous model will be parameterized carefully from atomistic calculations to yield quantitative results. The goal of this PhD project is to use this continuous approach to predict the yield stress of an alloy as function of the composition, temperature and strain rate. Comparison of these results with experimental data from literature will allow to validate the approach.
This PhD project relies on the use and development of numerical tools. Candidates are expected to show an interest for these numerical methods and to hold some experience in code development (e.g. C++, Python).
The PhD candidate will be integrated to the METAL team of Mateis lab composed of 20 permanent researchers and 30 PhD and postdocs working on links between processing, microstructure and properties in metallic alloy. Several numerical projects are currently ongoing.
Constraints and risks
No specific risks are associated with this project
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