Evaluation Of The Damage In The Stainless Steel Coatings By Residual Stress Measurement

Thin solids films of 304L stainless steel are prepared by the ion beam sputtering technique. The obtained films present a debonding phenomenon and a high compressive stress state. The critical stress value causing the debonding phenomenon is determined using atomic force microscopy (AFM). By ion beam assisted deposition (IBAD) process during the films elaboration, we observe a stress relaxation. This effect is measured using the X-ray diffraction method sin2Ψ.Thin solids films of 304L stainless steel are prepared by the ion beam sputtering technique. The obtained films present a debonding phenomenon and a high compressive stress state. The critical stress value causing the debonding phenomenon is determined using atomic force microscopy (AFM). By ion beam assisted deposition (IBAD) process during the films elaboration, we observe a stress relaxation. This effect is measured using the X-ray diffraction method sin2Ψ

Elastic anisotropy of polycrystalline Au films: Modeling and respective contributions of X-ray diffraction, nanoindentation and Brillouin light scattering

Elastic properties of non-textured and {1 1 1}-fiber-textured gold thin films were investigated experimentally by several complementary techniques, namely in situ tensile testing under X-ray diffraction (XRD), nanoindentation and Brillouin light scattering (BLS). Specimens were probed along different directions to reveal the strong effects of elastic anisotropy at the (local) grain and (global) film scales. XRD allows the investigation of both local and global anisotropies, while BLS and nanoindentation are limited to global analyses. A micromechanical model, based on the self-consistent scheme, and accounting for the actual microstructure of the films, is applied to interpret experimental data. Although different types of elastic constants can be determined with the used experimental techniques (static/dynamic, local/global), a good agreement is obtained, showing that comparison of these techniques is feasible when carried out carefully. In particular, the use of a micromechanical model to estimate the effects of the local elastic anisotropy at the film scale is unavoidable. The presented results show that XRD, BLS and nanoindentation should capture anisotropic texture effects on elastic constants measurements for materials with a Zener anisotropy index larger than 2. Conversely, the actual texture of a given specimen should be taken into account for a proper analysis of elastic constants measurements using those three experimental techniques

Plasticité des fils nanocomposites CuNb hyperdéformés : simulation et déformation in-situ sous neutrons et RX

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Cu/Nb nanocomposite wires processed by severe plastic deformation for applications in high pulsed magnets : effects of the multi-scale microstructure on the mechanical properties

International audienceCopper‐based high strength and high electrical conductivity nanocomposite wires reinforced by Nb nanotubes are prepared by severe plastic deformation, applied with an Accumulative Drawing and Bundling process (ADB), for the windings of high pulsed magnets. The ADB process leads to a multi‐scale Cu matrix containing up to N = 854 (52.2 106) continuous parallel Nb tubes with diameter down to few tens nanometers. After heavy strain, the Nb nanotubes exhibit a homogeneous microstructure with grain size below 100 nm. The Cu matrix presents a multi‐scale microstructure with multi‐modal grain size distribution from the micrometer to the nanometer range. In‐situ tensile tests of the nanocomposite wires under neutrons and high energy synchrotron beam shed light on the effects of the multi‐scale microstructure and internal stresses on their macroscopic elastic‐plastic properties, revealing that microstructure architecture offers an additional degree of freedom in the tailoring of materials properties

Oxidation of phosphated iron powders

The present work deals with the influence of phosphating treatment on the oxidation resistance of iron powders. Iron powders with particles diameter size of approximately 100 μm, have been immersed in phosphoric acid (0.102 mol l-1) in an acetone solution. After half an hour, a phosphate layer of less than 0.1 μm is formed at the metal surface. XRD spectrum is characteristic of an amorphous or nanocrystalline coating. The oxidation is performed by in situ thermogravimetric experiments in artificial air (20% O2-80% N2). For oxidation times of 24 or 48 h, between 350 and 700 °C the kinetics are recorded for both untreated and phosphated powders. At all temperatures, the phosphate acts as a protective barrier layer. Between 350 and 450 °C the coated powders present two parabolic stages in their oxidation kinetics and progressively with increasing temperature, the first stage disappears. On the other hand, uncoated iron powders show only one parabolic stage when oxidized. The oxidation constants kp were plotted for each stage of the curves vs. 1/T. From each Arrhenius plot an activation energy is deduced. For the phosphated powders, an activation energy of less than 0.6 eV is found in the first stage while for the second stage the deduced value of approximately 1.8 eV is the same that for the uncoated iron. That second parabolic stage for the coated powders can be compared with the oxidation of cast iron while in the first stage another mechanism may be involved. XRD studies of the oxidized powders at 350 °C for 48 h show that Fe3O4 and Fe2O3 are formed both on uncoated iron and on the coated powder. For phosphated powders, the amount of oxide is less important. As a result the phosphate layer acts as a diffusion barrier that slows down the oxidation of iron