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X‐ray Laue microdiffraction aims to characterize microstructural and mechanical fields in polycrystalline specimens at the sub‐micrometre scale with a strain resolution of ∼10−4. Here, a new and unique Laue microdiffraction setup and alignment procedure is presented, allowing measurements at temperatures as high as 1500 K, with the objective to extend the technique for the study of crystalline phase transitions and associated strain‐field evolution that occur at high temperatures. A method is provided to measure the real temperature encountered by the specimen, which can be critical for precise phase‐transition studies, as well as a strategy to calibrate the setup geometry to account for the sample and furnace dilation using a standard α‐alumina single crystal. A first application to phase transitions in a polycrystalline specimen of pure zirconia is provided as an illustrative example. [ABSTRACT FROM AUTHOR]

Wadsleyite is the dominant mineral of the upper portion of the Earth's mantle transition zone (MTZ). As such, understanding plastic deformation of wadsleyite is relevant for the interpretation of observations of seismic signals from this region in terms of mantle flow. Despite its relevance, however, the deformation mechanisms of wadsleyite and their effects on microstructures and anisotropy are still poorly understood. Here, we present the results of new deformation experiments on polycrystalline wadsleyite at temperatures of 1400-1770 K and pressures between 12.3 and 20.3 GPa in the laser-heated diamond anvil cell. We rely on multigrain X-ray crystallography to follow the evolution of individual grain orientations and extract lattice preferred orientations at the sample scale at different steps of the experiments. A comparison of experimental results of our work and the literature with polycrystal plasticity simulations, indicates that <111> {101} is the most active slip system of dislocations in wadsleyite at all investigated conditions. Secondary slip systems such as [001](010), [100](001), and [100]{0kl}, however, play a critical role in the resulting microstructures and their activity depends on both temperature and water content, from which we extract an updated deformation map of wadsleyite at MTZ conditions. Lastly, we propose several seismic anisotropy models of the upper part of the MTZ, depending on temperature, geophysical context, and levels of hydration that will be useful for the interpretation of seismic signals from the MTZ in terms of mantle flow and water content. [ABSTRACT FROM AUTHOR]

Laser annealing experiments are performed on cold rolled IF steel whereby highly localized microstructure and property modification are achieved. The microstructure is seen to develop by strongly heterogeneous recrystallization to provide steep gradients, across the submillimeter scale, of grain size and crystallographic texture. Hardness mapping by microindentation is used to reveal the corresponding gradients in macroscopic properties. A 2D level set model of the microstructure development is established as a tool to further optimize the method and to investigate, for example, the development of grain size variations due to the strong and transient thermal gradient. Particular focus is given to the evolution of the beneficial γ-fiber texture during laser annealing. The simulations indicate that the influence of selective growth based on anisotropic grain boundary properties only has a minor effect on texture evolution compared to heterogeneous stored energy, temperature variations, and nucleation conditions. It is also shown that although the α-fiber has an initial frequency advantage, the higher probability of γ-nucleation, in combination with a higher stored energy driving force in this fiber, promotes a stronger presence of the γ-fiber as also observed in experiments. [ABSTRACT FROM AUTHOR]

Abstract: The strongly anisotropic rheology of olivine polycrystals, associated to their microstructure, constitutes a key feature affecting the dynamics of the Earth''s upper mantle. High pressure deformation experiments carried out on olivine single crystals under synchrotron radiation, together with estimations of lattice friction based on first-principle calculations, show a transition from easy [100] to easy [001] slips as pressure and temperature (thus depth) increases. We input these data at the slip system level into the second-order extension of the self-consistent scheme to assess microstructure evolution along a typical flow pattern beneath an oceanic spreading center. [Copyright &y& Elsevier]

The microstructures induced by the laser-powder bed fusion (L-PBF) process have been widely investigated over the last decade, especially on austenitic stainless steels (AISI 316L) and nickel-based superalloys (Inconel 718, Inconel 625). However, the conditions required to initiate recrystallization of L-PBF samples at high temperatures require further investigation, especially regarding the physical origins of substructures (dislocation densities) induced by the L-PBF process. Indeed, the recrystallization widely depends on the specimen substructure, and in the case of the L-PBF process, the substructure is obtained during rapid solidification. In this paper, a comparison is presented between Inconel 625 specimens obtained with different laser-powder bed fusion (L-PBF) conditions. The effects of the energy density (VED) values on as-built and heat-under microstructures are also investigated. It is first shown that L-PBF specimens created with high-energy conditions recrystallize earlier due to a larger density of geometrically necessary dislocations. Moreover, it is shown that lower energy densities offers better tensile properties for as-built specimens. However, an appropriate heat treatment makes it possible to homogenize the tensile properties. [ABSTRACT FROM AUTHOR]

Abstract: An efficient full-field formulation based on fast Fourier transforms (FFTs) for the prediction of the viscoplastic deformation of polycrystals is applied to the study of the subgrain texture and microstructure evolution in polycrystalline Cu deformed under tension. Direct input from orientation imaging microscopy (OIM) images is used in the construction of the initial unit cell. Average orientations and misorientations predicted after 11% tensile strain are directly compared with OIM measurements, showing good agreement. The differences between misorientations of surface grains compared with bulk grains are estimated, and the orientation dependence of intragranular misorientations is studied. Measurements and simulations agree in that grains with initial orientation near 〈110〉 tend to develop higher misorientations. This behavior can be explained in terms of attraction towards the two stable orientations and grain interaction. Only models that account explicitly for interaction between individual grains, like the FFT-based formulation, are able to capture these effects. [Copyright &y& Elsevier]