Papers by Author: Jean Louis Soubeyroux

Abstract: In order to optimize the synthesis process of internal-Sn Nb3Sn wires, magnetization measurements have been performed on samples reacted at various temperatures between 650 and 725 °C and for time ranging from 8 to 200 h We compared samples of various origins, from NIN in Xi'an and Alstom in Belfort. These measurements give us access to critical and irreversibility temperatures. Although all Nb-Sn phases are superconductive, their critical temperatures are varying from 6 K (18at%Sn) to 18.3 K (25%atSn : stoichiometric Nb3Sn). Thus, Tc and T* measurements are related to the progress of tin diffusion and reaction in the wires. We correlate the results of magnetization with SEM (Scanning Electron Microscopy) and EDS (Energy Dispersive Spectroscopy) observations, which indicate directly the Sn content distribution across Nb filaments.

Abstract: The layer growth of the A15 (Nb3Sn) superconducting phase produced by the internal tin method on model monofilament wires was studied by neutron diffraction and electron microscopy techniques. Different ratios of the inner part of the wire (Sn/Cu) and the effect of the addition of 1% of zirconium to niobium were studied. The high temperature heat treatment plays a key role on the A15 formation and on the cost of the final wires produced. Different temperatures in the range 650-725°C and different annealing times in the range 8-200 hrs have led to the preparation of 72 different samples. The neutron diffraction study has evidenced the different phases formed during the heating treatment and the electron microscopy study has evidenced a power law for the growth rate of the A15 phase. In both studies the addition of zirconium in niobium is very effective on the growth rate of the A15 phase.

Abstract: New bulk metallic glasses (BMG) have been synthesized in the Mg-Cu-RE systems (RE= Y, Gd) with high critical diameter. In order to determine the glass forming range of these ternary systems, the calculation of the onset of driving forces (ODF) has been performed and has shown a large composition range for BMG formation. The synthesis of particular compositions in this domain has shown that all the produced alloys present a high glass forming ability (GFA) measured by DSC experiments. The ODF model, synthesized alloys by mould casting, characterization by X-ray diffraction and DSC techniques are presented.

Abstract: During the crystallization study of the bulk metallic glass 46.8Ti8.2Cu7.5Ni10Be27.5 (Vit4) we have demonstrated that the primary crystals appearing during isothermal annealing in the glass region, above Tg and before Tx, were of quasicrystalline nature and beryllium free. The formula of the quasicrystalline phase so obtained and determined by electron techniques (EDX and EELS) was Zr63Ti14.4Ni12.4Cu10.2. We have synthesized phases in the system Zr75-xTixCu25-yNiy by melt spinning and obtained either amorphous or quasicrystalline phases. For the amorphous phases, we have studied the crystallization by in-situ neutron diffraction and obtained quasicrystals as primary crystals. Neutron and X-ray diffraction, DSC studies are presented.