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Utilization of amorphous metallic alloy has received much attention for use in numerous microelectronic and electrochemical devices since they provide unique electrical, thermal conductivity, and magnetic properties. To develop these functional properties, it is essential to understand the amorphous structure and the property relationships. First principles calculations provide insight into the structure, thermodynamic stability, electronic and magnetic properties of amorphous alloys. For Ru- and Co-based alloys, the thermodynamic stability was examined by calculating the mixing energy along with those of crystalline counterparts. The amorphous RuP, CoP, RuB, and CoB alloys, become energetically more favorable than their crystalline counterparts at moderate P(B) content. The atomistic structures have well-defined local structures depending on the atomic size ratio and electronic interactions between constituent elements. Their local ordering is attributed to strong p-d hybridization, which contributes to stabilizing the Ru(Co)-P(B) alloys. Surface segregation of P(B) and interfacial adhesion with copper were also studied. Li-X (X: Si, Ge, and Sn) were examined when 1 or 2 Li atoms are inserted into the interstitial sites. Li insertion in the tetrahedral site, which is the most preferable site in the diamond matrix, causes outward displacement and charge localization around the X neighbors, thereby weakening of the covalent bonds leading to destabilization of the host matrix. We present the energetics, structure, electronic and mechanical properties of crystalline and amorphous Li-X (X: Si, Ge, Sn, and Si+Sn) alloys. Our calculations show that the incorporation of Li leads to disintegration of the tetrahedrally-bonded X network into small clusters of various shapes. Electronic structure analysis highlights that the charge transfer leads to weakening or breaking of X bonds with the growing splitting between s and p states, and consequently the Li-X alloys softens with increasing Li content. / text

Depuis leur découverte, un travail de recherche important a été développé sur la production, la structure, la microstructure, les propriétés et les applications des alliages métalliques amorphes. Cependant, la question de ce qui est entendu exactement par le terme « amorphe » n’est pas considérée dans la majorité des études publiées. Or, il n’existe pas de verres réels représentant un désordre parfait comme il n’existe pas de cristaux réels avec une structure parfaitement ordonnée. Il est difficile de donner une définition précise sans donner les limites d’échelle et la technique de détection de cette non-cristallinité. L’étude est une interrogation, pour un alliage particulier, sur le terme « amorphe » en fonction de l’échelle et de la technique. Cette étude comporte une analyse des conditions de préparation d’échantillons amorphes de mêmes compositions. Des techniques complémentaires de détection de leurs différences, en particulier à l’échelle de la structure et de la microstructure ont été utilisées. Des échantillons Pd82Si18 d’épaisseurs différentes ont été produits par solidification ultra rapide sur roue, avec différents paramètres, tels que la vitesse de rotation de la roue, la pression du gaz d’éjection, les dimensions de l’orifice d’éjection, la température de trempe et l’existence ou non d’un traitement thermique du liquide avant la trempe, etc. Les échantillons ont été ensuite analysés avec plusieurs techniques, telles que la diffraction des rayons X et des neutrons, la diffusion des neutrons aux petits angles, la microscopie électronique à transmission, la calorimétrie, les essais mécaniques, la fractographie par microscopie électronique à balayage / Since their discovery, an important research work has been developed on the production, the structure, the microstructure, the properties and the applications of amorphous metallic alloys. However, the question of what is exactly meant by the term “amorphous” is not considered in most of the reported studies. As a matter of fact, there exist no real glasses representing a perfect disorder, as there exist no real crystals with a perfectly ordered structure. It is thus difficult to give a precise definition without giving the limitations in scale and in detection of this non-crystallinity. The aim the study is an interrogation, in the case of a specific alloy, on the term “amorphous” as a function of the two directions of reference given above (the scale and the technique). This study thus contains an analysis of the conditions of synthesis of amorphous samples of similar compositions. Furthermore, complementary detection techniques of their differences at the scale of the structure and microstructure have been used. Samples of Pd82Si18 of different thickness have been produced by melt-spinning with different parameters, such as the rotation speed of the wheel, the pressure of the gas, the dimensions of the nozzle, the quenching temperature and the existence or not of a heat treatment of the melt before quench. The samples have been analysed by various techniques such as diffraction of standard X rays and of neutrons, small angle neutrons scattering, transmission electron microscopy, calorimetry, mechanical tests and fractography by scanning electron microscopy