The thesis is divided into three main parts. The first section summarizes the theory of the issue. Here we are unified theoretical information about the various possibilities of different approaches. The result of this part is therefore a general summary of theoretical possible procedures of creation bone implant, where each are listed the advantages and disadvantages. The theoretical part also contains information that ultimately, in practice, the author did not use. But his idea was to create a comprehensive look at the issue from several angles. The second part uses theoretical knowledge from the previous set of information as a basis for defining the steps required to successfully manage the issues of bone 3D printing. The third part will follow the guidelines of both previous and focuses on practical making bones and subsequent evaluation method chosen. There are discussed various steps that led to the final conclusion, making bones and work is then focused on the evaluation of the success of selected procedures and recommendations for future action.

Co-20Cr-15W-10Ni alloy (L-605) is a cobalt-based superalloy combining high strength with keeping high ductility, biocompatible and corrosion resistant. It has been used successfully for heart valves for its chemical inertia, and this alloy is a good candidate for stent elaboration. Control of grain size distribution can lead to significant improvement of mechanical properties: in one hand grain refinement enhance the material strength, and on the other hand large grains provide the ductility necessary to avoid the rupture in use. Therefore, tailoring the grain size distribution is a promising way to adapt the mechanical properties to the targeted applications. The grain size can be properly controlled by dynamic recrystallization during the forging process. Therefore, the comprehension of the recrystallization mechanism and its dependence on forging parameters is a key point of microstructure design approach. The optimal conditions for the occurrence of dynamic recrystallization are determined, and correlation between microstructure evolution and mechanical behavior is investigated. Compression tests are carried out at high-temperature on Thermec-master Z and Gleeble forging devices, followed by gas or water quench. Mechanical behavior of the material at high temperature is analyzed in detail, and innovative methods are proposed to determine the metallurgical mechanisms at stake during the deformation process. Mechanical properties of the material after hot-working and annealing treatments are investigated. The grain growth kinetics of L-605 alloy is determined, and experimental results are compared with the static recrystallization process. Microstructures after hot deformation are evaluated using SEM-EBSD and TEM. Significant grain refinement occurs by dynamic recrystallization for high temperature and low strain rate (T≥1100 ◦ C, strain rate < 0.1s−1), and at high strain rate (strain rate > 10s−1). Dynamic recrystallization is discontinuous and takes place from the grain boundaries, leading to a necklace structure. The nucleation mechanism is most likely to be bulging from grain boundaries and twin boundaries. A new insight of the modeling of dynamic recrystallization taking as a starting point the experimental data is proposed. By combining the results from the mechanical behavior study and microstructure observation, the recrystallization at steady-state is thoroughly analyzed and provides the mobility of grain boundaries. The nucleation criterion for the bulging from grain boundaries is reformulated to a more general expression suitable for any initial grain size. Nucleation frequency can be deduced from experimental data at steady-state through modeling, and is extrapolated to any deformation condition. From this point, a complete analytical model of the dynamic recrystallization is established, and provides a fair prediction on the mechanical behavior and the microstructure evolution during the hot-working process.

L’alliage L-605 est un superalliage base cobalt combinant une haute résistance et une bonne ductilité, de plus il est biocompatible et présente une bonne résistance a la corrosion. Dû a son inertie chimique dans le corps humain, ce matériau a été utilise avec succès pour fabriquer des valves cardiaques et des stents. Le contrôle de la microstructure peut influencer grandement les propriétés mécaniques : notamment un raffinement des grains est susceptible d’augmenter d’avantage la résistance et serait intéressant pour permettre de fabriquer des stents selon une architecture plus fine. L’ajustement de la distribution de taille de grains à travers le phénomène de recristallisation lors de la déformation à chaud apparait comme une solution pratique pour ajuster les propriétés mécaniques du matériau. Pour contrôler la microstructure et choisir les conditions de procédé optimales, les mécanismes mis en jeu lors de la recristallisation dynamique et l’effet des conditions de déformation sur la taille de grain doivent être compris et prévisibles par des outils théorique. Les propriétés mécaniques du matériau à haute température sont déterminées par des essais de compression à chaud. L’évolution microstructurale du matériau lors de la compression est analysée par microscopie optique et électronique (EBSD, TEM). Le phénomène de recristallisation dynamique continue est mis en évidence, et procède par nucléation de nouveaux grains aux joints de grain. La corrélation entre le comportement mécanique à chaud et l’évolution microstructurale est déterminée expérimentalement. Les conditions optimales de déformation impliquant la recristallisation dynamique sont déterminées, et la microstructure résultante est étudiée en détail. De nouveaux outils théoriques permettant de prévoir les conditions de recristallisation et d’extraire les paramètres physiques du matériau a partir des données expérimentales sont proposés. Enfin, la recristallisation dynamique est modélisée analytiquement, et permet de prédire le comportement mécanique et l’évolution de la taille de grain lors de la déformation. / Co-20Cr-15W-10Ni alloy (L-605) is a cobalt-based superalloy combining high strength with keeping high ductility, biocompatible and corrosion resistant. It has been used successfully for heart valves for its chemical inertia, and this alloy is a good candidate for stent elaboration. Control of grain size distribution can lead to significant improvement of mechanical properties: in one hand grain refinement enhance the material strength, and on the other hand large grains provide the ductility necessary to avoid the rupture in use. Therefore, tailoring the grain size distribution is a promising way to adapt the mechanical properties to the targeted applications. The grain size can be properly controlled by dynamic recrystallization during the forging process. Therefore, the comprehension of the recrystallization mechanism and its dependence on forging parameters is a key point of microstructure design approach. The optimal conditions for the occurrence of dynamic recrystallization are determined, and correlation between microstructure evolution and mechanical behavior is investigated. Compression tests are carried out at high-temperature on Thermec-master Z and Gleeble forging devices, followed by gas or water quench. Mechanical behavior of the material at high temperature is analyzed in detail, and innovative methods are proposed to determine the metallurgical mechanisms at stake during the deformation process. Mechanical properties of the material after hot-working and annealing treatments are investigated. The grain growth kinetics of L-605 alloy is determined, and experimental results are compared with the static recrystallization process. Microstructures after hot deformation are evaluated using SEM-EBSD and TEM. Significant grain refinement occurs by dynamic recrystallization for high temperature and low strain rate (T≥1100 ◦ C, strain rate < 0.1s−1), and at high strain rate (strain rate > 10s−1). Dynamic recrystallization is discontinuous and takes place from the grain boundaries, leading to a necklace structure. The nucleation mechanism is most likely to be bulging from grain boundaries and twin boundaries. A new insight of the modeling of dynamic recrystallization taking as a starting point the experimental data is proposed. By combining the results from the mechanical behavior study and microstructure observation, the recrystallization at steady-state is thoroughly analyzed and provides the mobility of grain boundaries. The nucleation criterion for the bulging from grain boundaries is reformulated to a more general expression suitable for any initial grain size. Nucleation frequency can be deduced from experimental data at steady-state through modeling, and is extrapolated to any deformation condition. From this point, a complete analytical model of the dynamic recrystallization is established, and provides a fair prediction on the mechanical behavior and the microstructure evolution during the hot-working process.