Description du sujet de thèse

Effects of thermo-mechanical-chemical treatments on the microstructure and surface functionalization by anodization of biocompatible titanium alloys

The choice of biomaterial and its surface functionalization strategy are crucial to ensuring both mechanical stability and high biocompatibility while allowing for better adhesion of surrounding cells to the surface.
For several years now, metal additive manufacturing techniques have been experiencing significant growth in the production of parts from metal powders in a number of fields (aerospace, aeronautics, medical, etc.). The Laser Powder Bed Fusion (LPBF) process is favored in the medical sector because it offers the possibility of producing complex, custom-made parts specifically adapted to the patient's situation. The characteristics inherent to this technique, such as high cooling rates and layer-by-layer fusion, result in parts with properties that differ from those traditionally obtained by machining, notably a rougher surface that can reach an Ra of several tens of microns depending on the parameters applied during manufacture. Recent studies have shown that a slight surface roughness is beneficial in promoting cell adhesion mechanisms in vitro [1] and in vivo [2]. These results are encouraging, but the surfaces of LPBF parts could be optimized through surface treatments to enhance this adhesion and contribute to the success of the restoration.
The current state of the art does not allow us to determine the ideal surface treatment solution, but anodic oxidation (or anodizing) appears promising [3].
The originality of this project lies in investigating the functionalization by anodization of smatated surfaces of a completely biocompatible alloy (TiNb) developed in situ using LPBF. This development method will enable us to modulate the chemical composition and overcome the constraints of commercially available titanium powder grades.
This doctoral project aims to investigate a combination of two surface treatments: chemical-mechanical treatment using ultrasonic shot peening (SMAT for Severe Mechanical Attrition Treatment) and electrochemical treatment (anodization). SMAT makes it possible to modify the micro-roughness of the surface, which would facilitate the formation and growth of nanotubes on the surface through anodization. The project will also explore another way: the ability of SMAT to optimize surface chemistry by integrating elements that promote catalysis and the germination of nanotubes on the surface. Finally, if the SMAT+anodization approach proves successful in terms of surface functionalization, this combination will eliminate the time-consuming machining/grinding step traditionally performed on a raw LPBF part.
To achieve this, the project has three complementary pillars aimed at improving the growth of nanotubes on surfaces. The first two (anodization parameterization and optimization of surface chemistry using SMAT) will be combined in a third component, which will investigate the coupling of SMAT+anodization and study the mechanisms of nanotube growth in order to leverage the advantages of each technique, thereby promoting the nanostructuring of surfaces. In each of these sub-parts, the results will be compared with those obtained from parts traditionally manufactured by casting.
Regarding the first pillar concerning anodization, an ANR 2026 project (OdonTi-Nob), led by Wafa Elmay, has been submitted on the functionalization of surfaces by anodizing biocompatible titanium alloy parts developed in situ using LPBF for prosthetic applications in dentistry. In parallel with the ANR project, the doctoral student working on this thesis would investigate the formation of nanotube growth mechanisms in relation to the microstructure/texture of the substrate. Recent work [3] has demonstrated the feasibility of anodizing mirror-polished TA6V-LPBF surfaces to form nanotubes on the surface. The influence of the anodizing protocol parameters on nanotube growth has been studied [3], showing a significant impact of the inherent microstructure of the process. Modulation of the chemical composition and/or the application of appropriate heat treatments will be studied in order to obtain the formation of a microstructure that promotes the growth of nanotubes on the surface.
Regarding the second pillar concerning SMAT, the ANR ICARUS FALL project (launched in March 2025) includes a study dedicated to modifying surface chemistry using SMAT in order to facilitate the deposition and growth of ZnO nanowires. It has already been established that this SMAT technique significantly reduces the surface roughness of parts manufactured by SLM by removing unfused powder particles, while increasing fatigue resistance by creating compressive stresses below the surface [4]. Leila Naïm's thesis, which begins in November 2025, will enable the configuration of the SMAT chamber to be modified so that the chemistry of the material to be embedded in the surface can be chosen (either by modifying the chemistry of the shot blasting beads or by adding powder from a third material to the chamber). The doctoral student working on this project will then use this modified chamber to chemically improve the surface of the parts in order to promote the germination and growth of nanotubes. In this way, the “chemical pollution” of the surface caused by the shot will become an asset by acting as a catalyst for the reaction.
This part of the project therefore aims to select the best catalyst, introduce it uniformly using SMAT on the surface and subsurface of the samples, to study its effect on microstructures (precipitate formation, phase stability, nanocrystallization, etc.) before and after heat treatment, and finally to control the mechanical properties induced on the surface compared to those at the core of the sample.
At the end of the thesis, a third and final pillar will focus on modeling and optimizing the alloy+process+SMAT+anodization combination. In this section, the optimized surfaces will be subjected to anodization in order to create nanotubes. The quality of this nanotube layer will be correlated with the underlying microstructure of the substrate. SMAT causes nanostructuring of the shot-blasted surface, which may or may not be associated by phase transformation depending on the chemistry of the alloy. The shape and growth of nanotubes on the substrate are highly dependent on its microstructure (Bravais lattice, orientation, texture, etc.) [3], this part of the doctoral study will focus on the link between microstructure and deposit quality. Modeling the effect of the input values of the various parameters will lead to the creation of an objective function weighting the final performance of the deposit. The aim of the doctoral project will be to select the most interesting parameters for each process and thus propose the most promising avenues for future research.

Contexte de travail

Candidate profile
The candidate must have a university degree (engineering and/or master's) that qualifies them to enroll in a doctoral program, as well as in-depth knowledge of materials science (metallurgy, mechanics) and the associated characterization methods. The multidisciplinary nature of the project as a whole (design, materials, microstructure, mechanics, surface) will require a good theoretical knowledge of the disciplines, a certain degree of autonomy, an ability to synthesize information, and a sense of coordination and planning. A keen interest in experimentation and a team spirit that allows you to integrate into the research team and interact easily with different people are additional assets for successfully completing this thesis.
Good oral and written communication skills in English are essential. Knowledge of French may be an advantage.

Host team and partners
The thesis will be carried out at LEM3 - Laboratory for the Study of Microstructures and Materials Mechanics in Metz and is part of its development and research projects. LEM3 is a joint research unit (UMR) affiliated with the University of Lorraine, the CNRS, and Arts et Métiers. Its activities are organized into three scientific departments:
Department 1 MMSV - Mechanics of Materials, Structures and Living Organisms;
Department 2 IMPACT - Microstructure Engineering, Processes, Anisotropy, Behavior; Department 3 TPRIOM - Thermomechanics of Processes and Tool-Material Interactions.
The doctoral student will be part of the “Development and optimization of processes related to microstructures” research area in Department 2 (IMPACT).

Doctoral school
As a doctoral student in France, you will be enrolled at the University of Lorraine and will be part of the C2MP doctoral school (Chemistry, Mechanics, Materials, Physics). You will have the opportunity to benefit from a wide range of training courses during your doctoral studies.

Application
Applications must be sent to supervisors by email before Monday, April 6, 2026. The email must include a resume, copies of master's/engineering transcripts (except for the final semester, which is still being validated at the time of application), and a cover letter related to the position.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.