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Reference : UPR3407-GUYDIR-005
Workplace : VILLETANEUSE
Date of publication : Thursday, July 15, 2021
Scientific Responsible name : Prof. Guy DIRRAS
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 15 October 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
As the population of modern societies ages and the risk of bone disease or bone injury increases, the need for a new generation of materials with superior biocompatibility and adequate mechanical properties remains a challenge. The metallic materials currently used for biomedical implants are titanium alloys (Ti6Al4V) or steels (CoCr), among others. It is now accepted that, despite their wide application in the medical field, these materials have some drawbacks: their mechanical properties are not optimized: high Young's modulus, 110 GPa, and 250 GPa, for Ti6Al4V and CoCr, respectively, compared to that of bone 30 GPa. In addition, their wear can induce the release of toxic elements (which can trigger the neurotoxicological effect of Al in the case of the Ti6Al4V alloy, and carcinogenic of Co in the case of CoCr alloys). Finally, from a strictly economic point of view, their machining in the form of implants requires several related metallurgical operations, including a significant loss of material.
Through new chemical compositions, based on metallic elements that are not harmful to the human organism, and original and versatile processes of elaboration and shaping, the work proposed within the framework of this offer is based on solutions of materials based on metal alloys exhibiting markedly improved mechanical and physicochemical properties compared to the materials currently used. The proposed solution is based on the development by additive manufacturing (powder bed fusion) of compositionally complex concentrated multi-element alloys (CCAs), including high entropy (HEA) alloys. The choice will be made on the TiNbZr-X system (X = Mo, Ta), a system likely to exhibit better biocompatibility with a modular Young's modulus.
This research work is carried out within the framework of the ANR project “CoCoA-Bio: ANR-20-CE08-0032” carried by the LSPM (Laboratory of Process and Materials Sciences, UPR CNRS, 3407, Sorbonne University Paris North) where the thesis takes place, in collaboration with the Z3DLAB SAS company an SLM expert.
The candidate will come from a Master 2 research or graduated from an MSE school with a strong focus on physical metallurgy/materials science / Mechanics of materials. He/she must have a first experience in metal additive manufacturing (including training) or in powder metallurgy in general (HIP, SPS…) and a practice of heat treatments. Finally, a scientific curiosity, great autonomy, and an ability to work within a multidisciplinary team (metallurgy, Materials chemistry, mechanics of materials) and physicists will be appreciated.
An SLM production of this system has already been achieved by our research group. The work to develop and optimize the fusion and thermal post-treatment parameters remains to be done to validate the final microstructure / mechanical properties relationship, before chemical and biochemical functionalization and implant production. Thus, after each development step by SLM and possibly optimization of the microstructures by hot isostatic compaction and controlled annealing, the resulting microstructures will be fully characterized (SEM-EBSD, TEM, DRX) and their mechanical behavior analyzed under different loading conditions, including fatigue within the framework of an international collaboration.
Constraints and risks
The LSPM is a Restricted Regime Zone, which induces a latency of at least 8 weeks between the selection of the candidate and the start of the mission
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