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International audience

International audience

This study focuses on the effect of carburization time on the structural and mechanical properties of low carbon XC20 mild steel (C. Wt.% 1 = 1.1%, at 910 °C at different carburization times of 2, 4 and 6 h. The results obtained show that XC20 steel (non-carburized) has a ferrite-pearlitic structure with a hardness and a Young’s modulus of the order of (150 HV, 26 KN/mm2). After carburization, the structure of the carburized layer is transformed in martensite (Fe γ) in which cementite (Fe3C) is imbricated. The depth of the carburized layer and the amount of carbon on the surface gradually increase with increasing carburization time. In addition, the carburized XC20 steel becomes hard and brittle where the hardness and Young’s modulus have been increased for a high holding time until reaching maximum values ​​(845 HV, 48 KN mm−2) after 6 h of carburization . However, the toughness of XC20 steel has been reduced from 163 to 40 J cm−2.

Replacement of toxic and expensive vanadium (V) in medical grade titanium alloys with cheaper and non-toxic elements such as iron (Fe) or niobium (Nb), is an important step forward in developing safer and less expensive biomaterials. Evaluating the effect of different process parameters such as the milling time on the properties of these newly developed alloys helps in understanding and controlling their behavior. Hence, in this study, the influence of ball-milling duration (2, 6, 8, 12 and 18 h) on crystalline structure, phase evolution, densification, and mechanical characteristics of biomedical nanocrystalline Ti-6Al-4Fe (wt. %) alloys is investigated. X-ray diffraction (XRD) confirmed that after 6 h of milling, aluminum (Al) and Fe completely dissolved into Ti matrix to form a solid solution of Ti (Al, Fe). XRD further revealed that the crystallite size decreased from 56 to 30 nm and the micro-strain increased with an increase in milling time. A decrease in porosity along with an increase in density is also observed for the alloys with increasing milling time. Moreover, the values of porosity obtained for the developed Ti-6Al-4Fe alloys ranged from 1 to 12 %, which is comparable to the porosity of one of the cortical bones making it a potential candidate for bone replacements. Microhardness measurements showed that the hardness of the Ti-6Al-4Fe alloys was greater than the hardness of the conventional Ti-6Al-4V alloys. It was observed that the Ti-6Al-4Fe alloy fabricated with the powders milled for 2 h showed the lowest value of Young’s Modulus. Milling time also had a significant effect on the surface roughness of the alloy samples, which showed a decreasing trend with increasing milling times.

International audience

International audience; Ce travail rejoint une étude de résistance à la corrosion par application des revêtements de nickel phosphore déposés sur un substrat en acier de carbone en comparaison avec une autre méthode de protection qui consiste à l’ajouter de l'inhibiteur en milieu agressif (3.5% NaCl) en utilisant la méthode électrochimique stationnaire (courbes de polarisations), puis en résultant les paramètres électrochimiques par l’utilisation des logiciels VoltaMaster4 et VoltaMaster1. Les résultats obtenus par la méthode électrochimique stationnaire montrent que l'efficacité inhibitrice augmente avec la concentration croissante d'inhibiteur pour atteindre des valeurs optimales pour une concentration de 10x10-5mol / l ainsi que le meilleur revêtement de nickel phosphore qui résiste bien à la corrosion est celui qui a élaboré à I = 0,10 A. La meilleure méthode de protection contre la corrosion de nos expériences est l'utilisation d'un revêtement composite nickel phosphore qui présente des valeurs minimales de densité de courant de corrosion et de potentiel de corrosion.

International audience; This study takes place in a context where the feed manufacturers have access to eco labeling databases which allow them to do eco design and produce feeds with less environmental impacts. First results of eco feed show substitutions between feedstuffs compared to standard feed. Therefore, the objective of this study is to identify the rebound effects of the production of eco feed for pigs if the practice becomes widespread in France. A mind map was built with 5 experts to identify in a qualitative way the panel of different consequences. We then focused on the one concerning the change of crop rotations to produce eco feed. We chose a virtual territory dedicated to produce the feedstuffs for a pig farm and assessed the environmental impacts by LCA using different functional units and perimeters. The situation with the production of eco feeds can appeared better or worse compared to the production of standard feeds. This work underlines the complexity of eco design and the limit to do it with data from attributional LCA. It is necessary to complete the databases by information to make the users aware of the rebounds effects invisible during the eco design process.

International audience

International audience

International audience; We became interested in this work to study the tribological behavior of two total hip replacements steel AISI 316L and titanium alloy Ti-6Al-7Nb tests performed in this work are essays with reciprocating movement. The tribological properties of wear by sliding (reciprocating) for the different samples were evaluated in the air on a tribometer with a tribotester software software following standards: ISO 7148, ASTM G99-95a, ASTM G 133-95, with a relative humidity of 33-38% at a temperature 24 to 27°C and a non-lubricated state. The ball 100C6 steel of 10 mm diameter, 835 HV hardness and Young’s modulus 310 GPa was chosen as the antagonist to prevent further chemical reactions. Three different speeds (1, 6 and 15 mms-1) and four normal forces (2, 4, 6 and 10 N) were applied, which allowed us to test twelve different conditions. The values of the friction coefficient obtained in this work are confirmed by the bibliographical results and meet the standards imposed by biomedical particularly at the joint surface state of hip prostheses.

The current research was undertaken to study the improvement of the tribological behavior of nanocrystalline bioceramic, α-alumina sample, produced by the calculations of gibbsite at different temperatures (300 to 1200°C), followed by uniaxial pressing, sintering and HIP treatment. The improved friction and wear resistance is attributed to the fine microstructure of the sample calcined at 1400 °C.