On the Deformation of Dendrites During Directional Solidification of a Nickel-Based Superalloy

Abstract: Synchrotron X-ray imaging has been used to examine in situ the deformation of dendrites that takes place during the solidification of a nickel-based superalloy. By combining absorption and diffraction contrast imaging, deformation events could be classified by their localization and permanence. In particular, a deformation mechanism arising from thermal contraction in a temperature gradient was elucidated through digital image correlation. It was concluded that this mechanism may explain the small misorientations typically observed in single crystal castings

Random angle grain boundary formation and evolution dynamics during Si directional solidification

International audienceThe growth of multicrystalline silicon and the formation of a random angle grain boundary, as well as the dislocation generation and expansion is observed dynamically in situ, by Synchrotron X-ray imaging techniques. The focus is kept on a random angle grain boundary since its behavior is particularly important to better understand the HP mc-Si (High Performance Multi-crystalline Silicon) photovoltaic properties. Due to the process conditions and to the grain competition that occurs during the solidification, a facetted {111} /facetted {111} groove is formed by this random angle grain boundary at the solid/liquid interface. It is shown how the shape of the solid/liquid interface allows the change of the preferential {111} growth facet and affects the grain boundary propagation direction. In one of the groove configurations, the two adjacent {111} facets do not have the same growth velocity and as a consequence the corresponding grain boundary does not follow the bisector of the angle between the two facets. Indeed, the direction of the grain boundary is determined by the growth velocities of the facets which control the grain competition. Moreover, under these experimental conditions a clear relationship is observed between the existence of random angle grain boundaries and the local generation of dislocations as well as their expansion. By comparison, dislocation emission is not observed at the level of Σ3 {111} grain boundaries

Spondylitis: a frequent and severe complication of infective endocarditis

Congress of the European-Society-of-Cardiology (ESC) / World Congress of Cardiology, Paris, FRANCE, AUG 31-SEP 04, 2019International audienc