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The load transfer induced by the elastic and plastic phase anisotropies of a Ti–10V–2Fe–3Al titanium alloy is studied. The microstructure consists in α nodules embedded in elongated β grains. EBSD performed on the alloy shows no crystallographic texture neither for α nor β phase. Tensile tests along the elongation direction, at a strain rate of 2 x 10-3 s-1 give a yield stress of 830 MPa with 13% ductility. Simulations based on an advanced two-phase polycrystalline elasto-viscoplastic self-consistent (EVPSC) model predict that the β phase first plastifies with a sequential onset of plasticity starting from oriented β grains, then and finally oriented β grains. This leads to a strong load transfer from the β grains to the α nodules whose average behavior remains elastic up to high stresses (~940 MPa). However, additional simulations considering exclusively β grains of specific orientation show that the behavior of α nodules is strongly dependent on the β texture in which they are embedded. Especially, in β grains, which plastify the latest, the model predicts the onset of plasticity in favorably orientated α nodules. Moreover, the orientation spread within the β grains can modify the average plastic behavior of α phase. In future, these results will be compared to data obtained from in-situ High Energy XRD and SEM/EBSD experiments.

Performing a complete in-situ strain measurement of polycrystalline thin films using X-ray diffraction is time consuming with most standard diffraction beamlines at synchrotron facilities and not realistic with laboratory diffractometers. Two dimensional detection is shown to enable relatively fast and reliable X-ray strain measurements during continuous in-situ tensile testing of metallic films deposited on polyimide substrates. We show in this paper the advantages to perform this kind of measurements as compared to those with punctual detection.

Transient effects in the creep of polycrystalline ice could play a crucial role for several ice flows (e.g. interaction between Antarctic ice shelves and ocean tides) and also have a major impact concerning deformation mechanisms of ice. During creep deformation of polycrystalline ice, strong stress and strain-rate intragranular heterogeneities are expected. These heterogeneities come from the very large viscoplastic anisotropy of ice crystals (with essentially a single easy plane for the dislocations to glide) which is responsible for the strong mechanical interaction between adjacent grains [1]. In order to go one step further in the quantitative understanding of this process, and to characterize the development of strain heterogeneities at a microscopic (intragranular) scale, we have performed deformation tests on 2-D polycrystalline ice exhibiting columnar grains with controlled grain size. Specimens were submitted to creep test and transient effects, in which both elastic and viscoplastic responses come in play, are investigated. A Digital Image Correlation (DIC) technique, with spatial resolution far smaller than the mean grain size, has been set to get continuous record of the intragranular displacement field during the test [2]. Experimental parameters have been optimized to improve the precision of the DIC results. In parallel, specimen microstructures were analyzed with an automatic ice texture analyzer, before and after deformation, and post-mortem measurements of local misorientations at the intragranular scale were performed. For the first time in ice, this work presents a direct link between grain orientation, strain localization, and lattice distortion at the intragranular scale.

The mechanical behaviour of multilayered W/Cu thin films on polyimide substrate has been investigated at different scales and using complementary X-ray techniques and compared to finite element analysis. Mechanical testing has been carried out using a new biaxial tensile machine which allows for testing in controlled biaxial loading condition. This device has been developed for synchrotron measurements at DiffAbs beamline of the French synchrotron radiation facility (SOLEIL, Saint Aubin).