The paper presents detailed analyses of solidification experiments performed on a refined Al-20wt.%Cu alloy using the SFINX (Solidification Furnace with IN situ X-radiography) laboratory facility. Directional solidifications of a sheet-like sample were carried out in a horizontal configuration, with the main surface of the sample parallel to the ground. The sample was solidified for a wide range of cooling rates to obtain various grain structures, from columnar to elongated and equiaxed. The formation of the grain structure was observed in-situ and in real-time by X-radiography, which allows the dynamic of solidification phenomena to be thoroughly analyzed. Based on the radiographs, quantitative measurements were performed to

Gravity effects such as natural convection in the liquid phase and buoyancy forces acting on the solid phase have a strong influence on the grain structure and microstructure formation dynamics during the solidification of metal alloys. It is thus very useful to undertake experimental studies that will provide benchmark data for a deeper understanding of the role of such gravity effects. In this paper, we study the formation of the equiaxed grain structure during refined Al-20wt.%Cu solidification in a temperature gradient for three different configurations: horizontal, vertical upward and vertical downward solidification. The key grain characteristics, namely grain size, grain elongation and grain growth orientation, were determined for all experiments and a comparative study was performed to identify the dominant effects of gravity 2 for each case. The present study provides quantitative information on the impact of grain flotation and solute flows on the equiaxed microstructure characteristics by means of in situ laboratory X-radiography.

On earth, gravity-related phenomena are unavoidable, such as thermo-solutal convection caused by density gradients in the melt and buoyancy when the liquid phase is denser than the solid phase. Such phenomena can drastically affect both the grain density and their morphology during equiaxed solidification processes. For these reasons, fundamental studies comparing the influence of solidification parameters with and without gravity effects are important to obtain benchmark data, which are useful to understand and then control the final structure of materials in industrial processes. In the present work, the impact of the solidification parameters on the dendritic grain structure formation and on the final grain size and shape was investigated in situ by using X-radiography for different growth orientations with respect to gravity. In a first step, experiments were carried out with various solidification parameters and with the furnace in horizontal position, with the main surface of the sample being perpendicular to gravity to limit gravity-related phenomena. In a second step, experiments were carried out with identical solidification parameters but with the furnace in a vertical position, and for two solidification directions (upward and downward). A comparative study between horizontal and vertical experiments was carried out. Phenomena related to gravity have been highlighted and their respective impact on the solidification front propagation was analysed.

The realization of an optical-fiber corrosion sensor (OFCS) has been achieved using two different methods. In the first method, a plastic clad silica (PCS) fiber whose uncladded part (2 cm in length) has been metallized through deposition using nickelphosphorus. In the second method, metallization used gold and nickel-phosphorus. The light power [PðÞ] at the exit end of the fiber is recorded as a function of the angle (, angle of incidence) made by the axis of the fiber and a beam from a laser diode at a 670 nm wavelength applied at the entrance of the fiber. It is observed that the corrosion of the coating material (nickel-phosphorus) modifies the PðÞ curves, be it by immersion in phosphoric acid solutions. The full width at halfmaximum of these curves increases with increasing corrosion pit density. Kinetic curves of corrosion have been obtained for different concentrations of phosphoric acid. This type of sensor is important because it can be inserted in metallic infrastructures to monitor the corrosion state of the structure in situ.

WC particles reinforced Fe-based metal matrix composites were synthesized by powder metallurgy process. The microstructure and composition of the specimens were analyzed and the wear-resistant properties against WC and alumina balls were comparatively investigated by SEM/EDS analyses. The wear rates of specimens were evaluated by optical profilometry. Microstructure exhibited austenite Fe-FCC dendrites, eutectic (iron austenite+carbides) and primary carbides. Two wear mechanisms have been identified from SEM as main mechanisms during dry sliding wear of Tungsten carbides reinforced iron matrix, namely oxidation and abrasion. The overall wear performance, which is obtained by considering the wear loss of the substrates, indicated less resistance against Alumina compared to WC ball contact.