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International audience; As part of a study devoted to the effect of trace elements on graphite degeneracy, near-eutectic ductile iron melts were prepared to which minute amounts of lead and of both lead and cerium were added. The melts were cast into an insulated Y4 mould, giving a solidification time of about 1 hour and a cooling time to room temperature of about 15 hours. In the thermal centre of the Pb containing sample graphite spheroids as well as intergranular lamellar graphite have been found. At the same location of the casting containing both Pb and Ce, exploded as well as chunky graphite could be observed, while the formation of intergranular lamellar graphite has been suppressed. Deep etching of the samples allowed reaching the following conclusions: i) intergranular graphite in the SG-Pb sample often, if not always, originates on graphite nodules and extends towards the last to freeze areas; ii) in one location of the SG-PbCe sample, chunky graphite strings were observed to originate on an exploded nodule, thus confirming the close relationship between these two forms of graphite. Because of the over-treatment in cerium of the SG-PbCe sample, other unusual degenerate graphite was observed which appears as coarse aggregates of "porous" graphite after deep etching.

The amount and alignment of hydroxyl ions influence the bioactivity of hydroxyapatite. Hydroxyl ions in hydroxyapatite are the most mobile and upon heating are the first to leave the lattice to form oxyhydroxyapatite. This work describes a method for producing hydroxyapatite with different amounts of hydroxyl ions, and reports on the changes in Fourier transform infrared absorption at increasing level of dehydroxylation. Detailed analysis of spectra in the 500 – 700 cm-1 range showed a peak shift for the hydroxyl ion absorption line at 632 cm-1 to 637 cm-1 and an increase in the wavenumber for the phosphate line at 575 cm-1.

© 2017 Trans Tech Publications, Switzerland. Calcium phosphate materials can be produced using a number of wet methods that are based on hydrothermal or co-precipitation methods that might use acidic or basic chemical environments. In our previously published works, we have investigated calcium phosphates such as monetite, hydroxyapatite, and whitlockite which were successfully produced by mechano-chemical methods and/or hydrothermal treatments from a range of marine shells and corals which were obtained from the Great Barrier Reef. The aim of the current work was to analyze and compare the mechanisms of conversion of one hard coral species and one calcified algae species from the Great Barrier Reef.

International audience; The repair of large bone defects is a major clinical problem for which tissue engineering (association of a biomaterial and cells) constitutes a valuable alternative. In this domain, the architecture and the mechanical properties of the 3D scaffold aimed to support cells is of key importance to succeed in bone reconstruction. In this study, we aim to design and evaluate a bionanocomposite foam-based scaffold, exhibiting all the desired biofunctional attributes of biocompatibility, bioactivity, osteoconduction/induction, combined with potential release properties. To perform this, 2 components have been associated: (i) a biopolymer, pectin, incorporating (ii) calcium phosphate nanoparticules to provide bone apatite nucleation sites, mechanical reinforcement, and to play the role of potential drug reservoir. The goal of this study was to determine the feasibility of obtention of such bionanocomposite by foam-templating, and to study the influence of mineral particules ratio on pectin foam and final scaffold 3D architecture and properties.

International audience; Amongst current aircraft research topics, morphing wing is of great interest for improving the aerodynamic performance. A morphing wing prototype has been designed for wind tunnel experiments. The rear part of the wing - corresponding to the retracted flap - is actuated via a hybrid actuation system using both low frequency camber control and a high frequency vibrating trailing edge. The camber is modified via surface embedded shape memory alloys. The trailing edge vibrates thanks to piezoelectric macro-fiber composites. The actuated camber, amplitude and frequency ranges are characterized. To accurately control the camber, six independent shape memory alloy wires are controlled through nested closed-loops. A significant reduction in power consumption is possible via this control strategy. The effects on flow via morphing have been measured during wind tunnel experiments. This low scale mock-up aims to demonstrate the hybrid morphing concept, according to actuator capabilities point of view as well as aerodynamic performance.

International audience; The biodegradable and biocompatible antibiotic containing thin film composites are very appropriate biomaterials as coating materials for dental implants because of their adjustable drug loading and release rates for the prevention of implant related infections. Coralline hydroxyapatite (HAp) was loaded with gentamicin antibiotics and combined with a biodegradable polylactic acid (PLA) to form thin film composites. PLA-HAp, PLA-Gentamicin (GM) and PLA-HAp-GM composites were produced, and their dissolution studies were carried out in phosphate buffered saline under SINK conditions. It was observed that the coatings could be efficiently applied to titanium dental implants and the drug release rates can be efficiently controlled.

International audience; Ti-β21S is a β-metastable titanium alloy, currently used in industries such as aeronautics, because of its cold formability, good mechanical properties at elevated temperature, low density and its strong resistance to oxidation. This alloy is hardened by an α-phase precipitation in the β-matrix. The purpose of the present research is to establish the effect of aging on the microstructure and mechanical properties of Ti-β21S. Different thermal aging tests have been carried out at 600°C and at 650°C for 500 hours in laboratory air. The evolution of the microstructure has been reported after each thermal treatment and associated with room temperature tensile tests results.

Thick composites are increasingly used in the design of mechanical structures. Combined with low weight, they are generally resistant structures, which can support importante loads. In addition, depending on the number and nature of the materials used, it is possible to adapt properties for specific applications (damping structures).This work proposes the establishment of a new theoretical model of multilayer beam. The model, which is simple and easy handling, is intended for the subsequent establishment of a finite element. The goals are:improve the refinement of the transverse displacement and transverse shear, avoiding the calculation of transverse shear, the use of correction factors,keep only the usual displacement,test the accuracy of the model compared with models from the literature (for an equivalent single-layer approach).The proposed approach is of the kinematics, the form adopted for the displacement field is justified from a dimensional point of view, by the equations of elasticity. The equations of motion and boundary conditions are obtained by applying the principle of virtual power.The validity of the model is tested on problems for which solutions (obtained by previous theories) exist.

Hastelloy X is a commercially available nickel-chromium-molybdenum superalloy with a good oxidation resistance, a good mechanical properties at high temperature and a significant formability; sine qua criteria for the choice of materials for the production of chambers turbojet combustion which is part of this study [1]. Arc welding technique is commonly used for the manufacturing of parts but the aeronautical requirements becoming increasingly severe especially in terms of reproducibility of geometry and metallurgical grade fillet weld. Laser welding is a viable method of assembly to meet these new demands by its automation to replace longer term the manual TIG welding. The high power CO2laser is extensively used for practical applications such as cutting and welding laser welding. The CO2laser is very used in the industry with regard to Yb:YAG laser which until now was not rather powerful but this changes. The aim of this study was to evaluate the effect of Yb:YAG laser beam parameters on the microstructure and mechanical properties of the laser beam welded superalloys Hastelloy X to define a field of weldability. The implementation of an experimental design approach is required due to the multitude of input parameters and the complexity of the phenomena involved [2-3].

Preface : The problem of contact materials subject to relative movement is becoming increasingly important for lifetime of the equipment, pollution and cost in energy. One of the aims of tribology is to understand how friction occurs and wear in dynamical contacts. This can vary considerably depending on the choice of the pair of materials and the experimental device. Few milligrams of material lost in a mechanism is sufficient to make it unusable and cause replacement with significant costs. There is still no specific and general formalism to solve the problem of tribology, that is to say, friction, tearing, wear and lubrication of solid and liquid. Friction behavior or wear depends on complex conditions of stress, environment and physicochemical properties of surfaces, themselves dependent on tribological mechanisms. The intrinsic mechanical properties of materials are complementary and play a direct role in the tribological process. The work presented at the ACMA’14 conferences are multidisciplinary, by interacting mechanics, physical chemistry and materials science on a different scale ranging, the goal is to explain, even if the reactions of the contact surfaces are very complex, the basics of tribology, the process of friction and wear, to apply the test methods on the materials in contact and get material coatings on other surfaces by different methods and processes mechanical, physical and chemical. This special issue of the journal "KEM: Key Engineering Materials" consists of a collection of studies both in the fields of experimental simulation of tribology than the science of surfaces in contact by relative movements in relation to the mechanical properties materials.

This work focuses on the acoustic emission signals related to three different tribological systems: a rotary sliding contact between WC-Co pins against alumina flat counterfaces, a fretting contact between alumina pins against alumina flat counterfaces and a reciprocating sliding flat on flat contact between thermoplastic polyurethanes (TPU) and a steel counterface. This document relates dependences observed between tribological behaviors and variations of acoustic emission signals. Therefore, a third body approach is used to explain these correlations and to highlight the aspect of nature and associated energy of acoustic emission sources.

Preface : The current economic and ecological context requires different industries towards the optimization of structures. One of the most striking examples is the soaring price of oil, which launched the major aircraft manufacturers Airbus and Boeing in a race to relief structures, to reduce their consumption. Therefore, the need of competitive products, both in terms of reliability, performance or operating cost, is pervasive and growing, aviation and elsewhere. Thus, work on the material parts by offering innovative solutions to reduce their weight and improve their performance (new materials, new processes, etc.) is essential and becomes more than ever a major industrial challenge. One way of increasing the selected aircraft is use of composite materials. Indeed, their high ratio mechanical / density properties and excellent resistance to environmental significantly improve the structural performance of the aircraft while generating a significant weight gain (20 to 30% weight of a structure). They were originally implemented in the design of secondary structures of aircraft, but improving their manufacturing processes and a better understanding of their mechanical properties and their degradation mechanisms are they now used for the manufacture of primary structures, such as the fuselage or the central box of an aircraft wing. If applications were rather the military origin, composites now particularly interested in civil aviation, the constraints are much stricter certification, which requires predictability of behavior and life of structures much finer Thus, at present, they account for over 50% of the mass of newer aircraft such as the Airbus A350, the Airbus A380 or the Boeing 787. The potential of composite materials is important, but will speak only on one condition: work not only on the basic constituents of the material (fibers, resin, ...) on the injection preparation conditions (methods, thermal cycle, shaped in the mold, ...) but also and above all on the function of the material in the structure. Indeed, the aterial is a component of a more complex system, consisting of parts, assemblies, subassemblies and the structure itself. This vision system involves understanding the material as parameters, not data, an overall optimization of the structure. This link between material and structure is evident for composites where fiber orientation, or reinforcements in a more general way, in the direction of efforts can greatly increase the performance / weight ratio. We understand that optimizing the structure requires, among other things, a design material to locally respond to the "just need" structural. The main objectives of this special issue (consisting mainly of a selection of papers presented at 5th International Symposium on AirCraft MAterials ACMA 2014) are, by means of modeling strategies and simulation out with conventional strategies, pushing the current limits in modeling and computation in response industrial and societal challenges. It is also to control the calculations and models in a framework that takes into account the major sources of uncertainty to optimize materials and structures. Particular attention is made to the modeling and validation of composite materials and structures.

This paper deals with an identification methodology of the interfacial fracture parameters to predict the lifetime of a metallic brazed joint. The methodology is based on an experimental-numerical study whereby the optimal parameters are obtained. The experimental data, using the scanning electron microscope analysis, allowed approving that failure of the assembly based AuGe solder seems first to appear near the interfaces. These results were confirmed by micrographs analysis of the solder/insert and solder/substrate interfaces. Then, using shear test results and parametric identification coupled with a finite elements model (FEM) simulation, the damage constitutive law of the interfacial fracture based on a bilinear cohesive zone model are identified. The agreement between the numerical results and the experimental data shows the applicability of the cohesive zone model to fatigue crack growth analysis and life estimation of brazed joints.

Aluminum 5-fold coordination coexisting with 4-and 6-fold coordination structurally characterizes amorphous aluminum oxide. For nearly 30 years now, 27Al MAS NMR has enabled to detect and later on to quantify this feature thanks to advances in high-resolution instrumentation. The Introduction shortly reviews the results of investigations of 5-coordinate aluminum in amorphous alumina through NMR analysis. Aluminum oxide is not a glass-forming oxide. A convenient way to obtain the amorphous state is by thin film deposition. We present here 27Al NMR analysis of a series of thin films of aluminum oxide prepared by metalorganic chemical vapor deposition (MOCVD) in the temperature range 360 ≤ Td ≤ 720 °C. In this range, low Td yield OH-containing films, while high Td yield nanocrystallites-containing films. The variation of the [4]Al, [5]Al and [6]Al content with Td is presented and discussed. It is correlated with the Td dependence of mechanical and corrosion protection properties. These properties are optimal when the structural disorder is to the utmost. Al coordination dependence on film thickness and the formation of metallic aluminum during the deposition process are also presented.

International audience; In the field of packaging, coatings are commonly applied on containers to avoid interactions between them and their content. For glass bottles, application of a thin film prevents interactions with the phase in contact and consequently the alteration of surface properties of the latter. In this article, we propose an innovative way to apply amorphous alumina coatings on glass bottles by metalorganic chemical vapor deposition from aluminum tri-isopropoxide. A numerical model, using the Computational Fluid Dynamics code FLUENT, has been developed to calculate local profiles of gas flow, temperature, concentration and deposition rates into the reactor. The submicrometric alumina films have been deposited at reduced pressure between 480°C and 670°C. Uniform thickness profiles have been determined on cross sections over the length of the bottle and have been successfully simulated. Strongly improved hydrolytic resistance with regard to the uncoated bottles reveals the excellent performance of the films.

The 2xxx serie aluminum alloys are characterized by good mechanical performances and low density, however they are susceptible to different forms of localized corrosion: pitting corrosion, intergranular corrosion and stress corrosion cracking. The 2024-T351 aluminum alloy is used in the aircraft industry for numerous applications such as fuselage and door skin. Corrosion damage of the material is also very detrimental for the structural integrity of the aircraft. The presence of coarse intermetallic particles, with a heterogeneous size distribution was found to be responsible for the 2024 susceptibility to localized corrosion. These particles are generally the cause of initiation sites. Presence of micro-defects in the oxide film upon coarse intermetallic particles and the galvanic coupling with the matrix contribute to the development of pitting corrosion. The over-ageing treatment (T7) is supposed to stabilize the microstructure and the mechanical properties to improve the corrosion resistance. The 2024 alloy microstructure after the T7 heat treatment remains very complex. The 2024 alloy corrosion behavior was studied in the over-ageing state for three different temperatures (150, 175 and 190 °C). During the corrosion tests in chloride-containing environment, the behavior of coarse intermetallic particles was found to be different. Thus, the 2024 samples suffer a gradual attack upon S-Al2CuMg particles and finally Al (Cu,Mn,Fe,Si) particles. The corrosion damage was studied by Atomic Force Microscopy (AFM) and Kelvin probe Force Microscopy (KFM). This technique allows simultaneous topographical and electric potential mapping to be obtained. This latest potential was shown to be correlated to the corrosion potential of the 2024 alloy. This study focuses on the variation of the KFM potential of the coarse intermetallic particles and the matrix for the over-ageing conditions (T7). Observations using optical microscope and AFM were also performed to obtain the corrosion rate for each condition. The corrosion rate was correlated to the chemical composition variation of the particles obtained by scanning electron microscope observations and EDS analyses.

In the field of advanced ceramics, Spark Plasma Sintering (SPS) is known to be very efficient for superfast and full densification of ceramic nanopowders. This property is attributed to the simultaneous application of high density dc pulsed current and load, even though the sintering mechanisms involved remain unclear. In the first part of the paper, the mechanisms involved during SPS of two insulating oxide nanopowders (Al2O3 and Y2O3) are discussed while in the second part illustrations of the potential of SPS will be given for (i) Consolidation of mesoporous or unstable nanomaterials like SBA-15 or biomimetic apatite, respectively; (ii) Densification of core (BT or BST)/shell (SiO2 or Al2O3) nanoparticles with limited or controlled reaction at the interface. (iii) In-situ preparation of surface-tailored Fe–FeAl2O4–Al2O3 nanocomposites, and finally (iv) One-step preparation of multilayer materials like a complete thermal barrier system on single crystal Ni-based superalloy.

Electronic power modules devices are paramount components in the aeronautical, automotive and military applications. The solder layers are the most critical parts of the module and are usually subjected in their whole life to complex loading conditions. To improve the design task, realistic thermoelastoviscoplastic and lifetime prediction models which can describe efficiently the deformation-damage of the electrical device must be chosen carefully. Some of the most common behavior models are based on the separation between creep and plasticity deformations such as power law, Garofalo, Darveaux… So, to take into account the creep-plasticity interaction, the thermal cycling as well as the hardening-softening effects, unified viscoplastic models are increasingly being used to describe more efficiently the physical state of the material. We propose in this framework a survey of some unified viscoplastic models used in the electronic applications for the viscoplastic modeling of the solder as well as creep-fatigue life prediction rules. The models are used for the characterization of a SnAgCu solder and are briefly compared within tensile, creep data and stabilized responses.

International audience; The ACCENT Project (FP7- AAT- 2007- RTD-1) will allow the European Aero Engine manufacturers to improve their competitiveness by applying adaptive control techniques to the manufacturing of their components. For the critical rotating parts of aircraft engines, the surface integrity generated after machining is a key factor on the life cycle. In this context, one particular attention has to be carried out on tool condition. The aim of this paper is to define a monitoring approach able to detect the tool condition and machining disturbances. The main failure modes characterizing this particular Nickel base drilling and the apparition of embedded chips over the machined surface were identified. By experimental techniques, cartography of failure modes was performed. The results show that flank wear and notch are the main failure modes limiting the tool life. For some cutting conditions, the tool failure occurs after the first hole due to the important cutting forces. Some interesting combinations are made between the spindle current/accelerometers/ thrust force and flank wear, tool breakage and notch. Before these correlations, a detailed signal analysis was performed, considering different disturbing phenomena, such as chips evacuation problem. Finally, a "synopsis" for process monitoring is proposed, considering the analyzed phenomena.

International audience; FUSCOMP (FUSelage COMPosite) is a Research & Development program which has received the label from the Aerospace Valley competitiveness cluster. It will lead to a test of a composite fuselage demonstrator manufactured by the Liquid Resin Infusion (LRI) process. LRI is based on the moulding of high performance composite parts by infusing liquid resin on dry fibers instead of prepreg fabrics. The study of this proof of concept is based on the TBM 850 airframe, a pressurized business turboprop aircraft currently produced by DAHER-SOCATA. Technical achievements will concern numerical methods and finite elements analysis to be used for the modelling of this aircraft composite fuselage structure. Actual industrial projects face composite integrated structure issues as a number of structures (stiffeners,...) are more and more integrated onto the skins of aircraft fuselage. Indeed the main benefit of LRI is to reduce assembly steps which lead to cycle time gain and thus cost reduction. In particular, infusing components and sub-components at the same time avoids riveting parts altogether. However it is necessary to validate the dimensioning of the studied composite structure.

The aim of this work is to identify parameters driving constitutive equations of materials with displacement field measurements carried out by image stereo-correlation during an unidirectional tensile test. We evaluate two identification techniques. The first one is the virtual fields method which consists in writing the principle of virtual work with particular virtual fields. It is generally used in the case of linear elasticity and it requires a perfect knowledge of the model in terms of boundary condition since the virtual fields used must be kinematically admissible. This method allows to determine parameters by a direct and fast calculation, without iterations. The second method is the finite element model updating method. It consists in finding constitutive parameters that achieve the best match between finite element analysis quantities and their experimental counterparts. This method is more adaptable than the virtual field method but it needs to spend more calculation time.

International audience; A common problem in the aeronautical industry is the chatter vibration due to the lack of dynamic stiffness in the milling of thin walls and thin floors. The present work proposes a method for chatter avoidance in the milling of flexible thin floors with a bull nose end mill. It allows the calculation of the thickness previous to finish milling or the minimum dynamic stiffness that the floor must have to avoid the chatter vibration appearance. To obtain these values, the stability model algorithm has been inverted to estimate the thickness or the dynamic stiffness required in a floor to allow a stable milling. This methodology has been validated satisfactorily in several experimental tests.

The first aim of this study is to analyze the impact behavior of pre-loaded composite. Indeed, a bi-axial load is applied to the composite specimen, in order to keep in touch with a real case of composite fuselage. Then, this pre-loaded specimen is impacted by a pendulum. The used energy and velocity are weak in order to be in the case of low-energy and low-velocity impact. The second aim of this study is to develop and design a pendulum device to be integrated to the bi-axial fatigue loading. Moreover, two Non Destructive Inspections (Sonoscan and InfraRed Thermography) is used in order to establish links between pre-load and induced impact damage.

The aim of this study is to gain knowledge concerning the process and its physics, as well as to become able to optimize the fabrication of large and complex composite parts in aeronautics appli- cations. Composite materials have many advantages and the use of this technology is increasing in the aeronautic industry. In the L.R.I. process, dry textile preforms are impregnated by a thermoset liquid resin. All the elements are enclosed in a vacuum bag of known pressure. Once preforms are totally impregnated, the resin system begins the curing reaction to obtain the composite part. This study contains two major sections. Firstly, numerical modeling was done with the Pam- Rtm nite element code to determine the evolution of the ow front during the infusion. Simulations were performed to analyse the infusion of sandwich composite parts with a perforate foam, which allows the inferior skin to be impregnated in the same operation. Secondly, experimental work was conducted to conrm the numerical results.

International audience; The fusion zone of an electron beam welded Ti-6Al-4V alloy presents a a' martensitic structure which leads to a change of mechanical properties. Starting from two manufacturing processing routes for the alloy (1) a b processing followed by the weld (which will be considered as the reference microstructures), (2) an a+b processing followed by welding and a post weld heat treatment (PWHT), the microstructure can be adjusted to avoid local difference of strength, fatigue properties and impact toughness. This results from the optimisation of the process and of the PWHT. The present work investigates the mechanical behaviour and the damage mechanism of both base metal and fusion zone in regards to the microstructure and to the heat treatment parameters.

International audience; In aerospace industry, the manufacturing of critical parts (high energy components) requires an important validation process to guarantee the quality of the produced parts, and thus their fatigue lifecycle. Globally, this validation consists in freezing the cutting conditions using metallurgical analysis or fatigue trials, and a test on the first article. This process is extremely complex and expensive. In this way establishing the correlation between the cutting conditions and the surface integrity will help us to optimize the manufacture of those parts. In this article, by the means of an experimental method, we define a domain of validation by combining the cutting conditions according to the classic criteria established by AFNOR E66-520 norm (Couple-Tool-Material) and the criteria of surface integrity for the drilling of a Nickel-base superalloy. The experimental device consists in drilling a Ø15.5 mm hole on a 3-axis milling centre instrumented by a 4 components Kistler dynamometer (Fx, Fy, Fz and Mz), a spindle power sensor "Watt-pilote" and three accelerometers placed following the directions X, Y and Z. Scanning Electron Microscopy (SEM) observations, micro-hardness tests and topographic measurements with an optical profilometer, are carried out to characterize the metallurgical state of the holes manufactured. Finally, correlations were respectively made between the cutting conditions, the recorded signals and the metallurgical state of the holes.

The purpose of this work is to study the Iosipescu shear test and more precisely its ability to characterize the shear modulus of a carbone/epoxy composite material. The parameters influencing this identification are the fibre orientation, the geometry of the notch and the boundary conditions. Initially these parameters were studied through the finite element analysis of the shear test. Then, the measurement of the shear strains was carried out by traditional methods of measurement (strain gauges) but also by optical methods. These optical methods: the digital image correlation and the electronic speckle pattern interferometry (ESPI); allow for various levels of loading, to reach a full-field measurement of the shear strain. This enabled us to study the strain distribution on the section between the two notches. The finite element model enabled us to study the parameters influencing the calculation of the shear modulus in comparison with strain gauges, image correlation and ESPI. This work makes it possible to conclude on optimal parameters for the Iosipescu test.

Magnetic susceptibility measurements, magnetization and neutron diffraction results at low temperature for cobalt and manganese oxide spinel ceramics are presented. The Curie temperature varies similarly with the sample composition in ceramics and powders. The experimental molar Curie constant variation is explained by the presence of Co2+, CoIII, Mn3+ and Mn4+, and possibly Co3+ in the octahedral sites for the cobalt rich phases. The magnetic moments of the cations in tetrahedral and octahedral sites are not collinear and the global magnetization is oriented in a third direction.

International audience; Both thermal analysis (TA) and differential thermal analysis (DTA) have been used since long to evaluate latent heat release and solid fraction evolution during solidification of metallic alloys. TA makes use of cooling curves recorded under "natural" cooling while DTA consists in recording the temperature difference between the sample temperature and an inert reference during a controlled cooling, i.e. at imposed constant cooling rate. In both cases, the solid fraction evolution is deduced from a calculation of the latent heat release as estimated by means of a heat transfer model. This paper provides a comparison of such evaluations performed on one Al-Si alloy.

In the present study we examine the crystallographic structure of the , ’’ and  phases present in nickel base 718 alloy. The chemical ordering of Nb atoms and possible planar faults that may be observed in ’’ precipitates are detailed. High resolution transmission electron microscopy (HRTEM) observations of various faults are reported. The decomposition of a matrix dislocation to form a locked V shaped configuration is shown. The observation along [110] type direction allows to identify the type of defect, which is observed as a pure geometric stacking fault.

The influence of post-inoculation and of cerium and antimony additions on the solidification process and on the formation of chunky graphite in ductile iron heavy-section parts have been studied previously in the case of near-eutectic alloys. It appeared of interest to complement these works by analysing the effect of carbon equivalent on graphite degeneracy. In the present work, hypo-, hyper- and near-eutectic melts have been cast in large blocks and standard cups. Analysis of the corresponding cooling curves recorded during solidification as well as microstructure observations on these casts have been carried out. A clear effect of carbon equivalent as promoter of chunky graphite formation is observed. The results have been added to the set of data already available and various correlations are discussed.

Through a few examples, we present a short review on properties and applications of TiO2 films deposited by various CVD processes. The constraints due to the growth process make difficult optimization of properties that were correlated with microstructures. We focus on the photocatalytic activity in the visible range and on the antibacterial behavior of these functional thin layers.

International audience; The aircraft industry uses materials more and more efficient. This trend affects the majority of parts such as structure parts. Titanium alloy (Ti-5AL-5Mo-5V-3CR) is now used for the production of landing gear. There are many goals in this paper. First, the physical and mechanical properties of the material will be presented. Secondly, we show the relationship between material properties and machinability. Third, the Ti5553 will be compared to Ti64. The Ti64 is a+b alloy group and Ti5553 is a metastable beta but we have chosen to compare these two materials. Ti64 is the most popular of titanium alloys and many of works were been made on its machining. After, we have cited the Ti5553 properties and detailed the behaviour laws. They are used in different ways, with or without thermal softening effect or without dynamic terms. We have to define the best model to use in cutting force model. Differents models are compared for two materials (steel and titanium alloy). To define the model, two methods exist that we have compared. The first is based on machining test however the second on Hopkinson bar test. These methods allow us to obtain different ranges of strain rate, strain and temperature. This comparison will show the importance of a good range of strain rate, strain and temperature for behaviour law, especially in titanium machining.

A diffusion barrier based on a NiW electrolytic coating has been developed to limit interdiffusion between a Ni-base superalloy (MCNG) and a β-NiAl bondcoating. Isothermal oxidation tests of 50h at 1100°C confirmed that W-rich layer formed with NiW coating modifies the oxidation behaviour of the bondcoat and limits interdiffusion. The diffusion barrier reduced β-NiAl γ’-Ni3Al transformation in the bondcoating and prevented SRZ formation.

The interaction of calcium phosphates with biological molecules under controlled conditions permits the formulation of meaningful conclusions concerning the driving forces. The uptake and release at the material-solution interface is the result of the various interactions between and within the system components which include the solid surface, the adsorbate, the solvent and other solutes present. The understanding of adsorption and desorption mechanisms with respect to active molecules can be exploited for the development of drug delivery applications.

International audience; Apatite/β−TCP particles exhibiting non-conventional urchin-like morphology were prepared by hydrothermal synthesis. Their implantation in the rat calvarium was followed during 60 days. A total absence of osteoconduction was observed despite a favorable chemical composition, stressing the fundamental role of particle morphology on bone regeneration. Results are discussed in relation with other literature data. Possible explanations include the disfavored accumulation of biological mediators due to the acicular shape of the particles and/or a limited accessibility for cells.

The corrosion resistance of MOCVD Al2O3 coating system was investigated to protect a TA6V Alloy under hot salt corrosion conditions: This coating was corroded with a salt deposit without mechanical loading at 480°C during 100 h. Corrosion products formed in salted areas were studied by Energy Dispersive Spectroscopy (EDS). Although all coated specimens were damaged with corrosion products presence in salted area, Al2O3 coatings showed the lowest salt damage on titanium substrate after a metallographic cross section observation compared to uncoated ones. As well as these interesting experimental results, coated specimens exhibit a good adherence on titanium substrate.

During service, TBC can suffer degradation by CMAS, FOD, erosion or spallation. Whereas the first three are due to foreign particles, the last one is related to thermal cycling. When subjected to high temperature exposures followed by rapid coolings under oxidizing conditions, a TBC system undergoes morphological changes and stress development. This will initiate cracks which propagate and finally lead to failure by spallation. Consequently, the aim of the present study is to understand better the mechanisms responsible for such spallation events. Two kinds of TBC systems with different bond coatings (NiCoCrAlYTa or Pt-modified nickel aluminide bond coatings) are thermally cycled. Subsequently, SEM investigations on TBC systems after spallation concentrate on failure path, defect, morphological and microstructural changes to propose way for improving TBC system lifetime.

Two Ni-Fe-Cr ternary alloys have been oxidized in simulated pressurized water reactor primary water at 360°C for 1000 h. The chemical composition of those alloys were chosen in order to be representative of the one of chromium depleted areas under the oxide scale of industrial alloys (e.g. alloy 600) exposed in the same conditions. The resulting oxidized structures (corrosion scale and underlying metal) were characterized using complementary analytical methods (FEG-SEM, TEM, SIMS, optical microscopy). On the one hand, the characterized external oxide layer is very close to the one observed on industrial nickel-base alloys, hence validating the use of such model alloys. On the other hand, both free oxygen and oxides have been detected at grain boundaries several micrometers under the metal/oxide interface. Implications of such a finding on the involved transport mechanisms for oxygen and the intergranular stress corrosion cracking resistance of nickel-base alloys are then discussed.

Alloy 718 is known to be sensitive to oxidation assisted intergranular cracking. It is also demonstrated that the occurrence of jerky flow (also called Portevin-Le Châtelier effect) stops the intergranular damaging mechanism. As dynamic strain ageing is known to be linked with the alloy content of interstitial species, the aim of the present work is to study the effect of carbon, nitrogen and oxygen concentrations on the mechanical behaviour of thin tensile specimens tested under oxidation conditions close to those encountered industrially for turbo machine disks. Thanks to heat treatments performed under reducing atmosphere, the content of interstitial species in tested alloy 718 samples is gradually curbed. Tensile specimens were then tested between 550 and 700°C for the strain rate range [10-5, 10-1] s-1. The key point of this work is that, for a given testing temperature, the tensile tests clearly demonstrated that the transition from an intergranular fragile fracture mode to a transgranular ductile one was always linked with the occurrence of Portevin-Le Châtelier phenomenon but for slower strain rates in comparison with what was observed on the as received aged material tested in the same conditions. This shift of the transition of fracture mode through the lower strain rates remained true until a threshold value of the heat treatment time under reducing atmosphere. Specimens heat treated over this value systematically exhibited a fully transgranular ductile fracture mode, whatever the plastic flow regime was. Implication of such a finding on the intergranular embrittlement of alloy 718 by high temperature oxidation is then discussed.

Alumina thin films were processed by MOCVD from aluminium tri-iso-propoxide, with N2 as a carrier gas, occasional addition of water in the gas phase, deposition temperature in the range 350-700°C, total pressure 0.67 kPa (2 kPa when water was used). The films do not diffract Xray when prepared below 700°C. At 700°C, they start to crystallize as γ-alumina. EDS, EPMA, ERDA, RBS, FTIR and TGA revealed that films prepared in the range 350-415°C, without water in the gas phase, have an overall composition Al2O3-x(OH)2x, with x tending to 0 with increasing temperature. Al2O3 is obtained above 415°C. When water is added in the gas phase, the film composition is Al2O3, even below 415°C. Coatings deposited in these conditions show promising protection properties.

The solidification and solid-state phase equilibria of four Al-Mg-Si alloys containing 30- 70%Mg and 0.5-3.5%Si, selected on the basis of an isothermal section of the Al-Mg-Si system calculated at 300 °C, have been investigated. Solidification paths of Mg-rich Al-Mg-Si alloys finish on ternary eutectics and the temperatures of two of these eutectic reactions, i.e. L↔(Al)+β+ Mg2Si and L↔(Mg)+γ+ Mg2Si, have been determined to be at ~ 448 °C and ~ 436 °C respectively by DTA. The characteristic temperatures recorded on the DTA curves are analysed and a linear relationship is found between the peak temperature and the square root of the scanning rate.

Calcium phosphates (Ca-P) are major constituents of calcified tissues, and are also extensively used for the elaboration of biomaterials. However, the usual high-temperature sintering processes generally lead to strong alterations of their chemical, physical and biological properties. Spark plasma sintering (SPS) is a non-conventional sintering technique based on the use of pulsed current, enabling fast heating and cooling rates, and lower sintering temperatures are often observed. The sintering of several orthophosphates (DCPD, amorphous TCP, beta-TCP, OCP, HA and biomimetic nanocrystalline apatites) by SPS was investigated in order to track potential advantages of this technique over usual Ca-P sintering methods. Special attention was given to the SPS consolidation of highly bioactive nanocrystalline apatites.

Isothermal oxidation of pure iron has been performed in air at atmospheric pressure between 260°C and 500°C. Growth kinetics are accurately analysed and scale morphologies are investigated by SEM and TEM observations. The calculation of the variations of the parabolic rate constant kp with scale thickness allows a better understanding of scale growth mechanisms involved at this intermediate temperature range, which have been poorly investigated up to now. These results are discussed with the objective of long term behaviour for long term interim storage of some nuclear waste containers.

A multiscale study of the high temperature oxidation effects on high purity polycrystalline nickel behaviour is presented. In situ tensile tests have been carried out at room temperature on preoxidised thin foils. The results obtained lead to a better understanding of the strengthening effect of the oxide layer. Detailed examinations of the metal microstructure are also made after high temperature oxidation treatment. Atomic Force Microscope (AFM), Secondary Ion Mass Spectroscopy (SIMS), Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) are used to characterise the microstructure. Formation of voids at grain boundaries as well as vacancy injection are then discussed.

When testing the resistance to oxidation of high temperature materials, the cyclic oxidation test is used as a reference because it integrates isothermal oxidation kinetics, oxide scale adherence, mechanical stresses, metallic alloy and oxide mechanical behavior and their evolution with time, in conditions close to the actual conditions of use. To fill the gap between the measurements of physical data (oxidation kinetics, interfacial energy, oxide toughness, growth stresses, coefficients of thermal expansion, mechanical properties of the alloy under the oxide scale,...) and the cyclic oxidation test, comprehensive scientific work is necessary, but also technological development and understanding of the practice of the cyclic oxidation test. This paper presents a new experimental tool, which allows the simultaneous measurement of the mass of several samples placed in the same controlled atmosphere during fast thermal cycles. This multi-sample thermobalance is described, in association with the description of the measurement methodology (i.e. “cyclic thermogravimetry”). First tests of performance of the apparatus are given, including heating and cooling rates and continuous Samass measurements for a P91 alloy.

International audience; 'Metal dusting' is a catastrophic disintegration of metals (Fe, Ni, Co)occurring in carburizing atmospheres typical of reformer plants, direct reduction plants, and many chemical and petrochemical processes.