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Étude métallurgique et optimisation de la fabrication d'alliages à base de cuivre coulés en continu : analyse de la ségrégation et des phénomènes de précipitation dans les alliages CuNi15Sn8, CuNi6Si1.8Cr, CuTi3Al2 et CuTi3Sn2.75

Abstract : The copper-beryllium alloys characterized by a structural hardening present mechanical properties close to those of high steels (Rm#1230MPa, Re 0.2#1060MPa, A%#6.5). On the other hand, they present high thermal and electric conductivities (22%I.A.C.S), a good resistance to wear and to corrosion, and they are non magnetic. The conjugation of these different properties enables Cu-Be alloys to find a broad range of applications (brake discs for planes, welding electrodes, spring Bumblebee for manometer etc). However, in addition to the cost raised by béryllium, the main inconvenience of these alloys is the presence of the beryllium oxide that is harmful when it is inhaled as powder or fume. In spite of all precautions that can be taken during the processing of these materials, the risk stays. Thus, to preserve healthy environmental conditions, a politic of research of substitute alloys having physical and mechanical properties as remarkable as those of Cu-Be alloys has been led. On the basis of a literature survey, two main families of copper rich alloys can be distinguished for their mechanical properties similar to those developed by Cu-Be alloys: the Cu-Ni-X (X=Sn, Si) and Cu-Ti-X(X=Al, Sn) systems in the rich copper side. Nevertheless, these alloys are not exempt of problem. For example, during the solidification processing by continuous casting, tin segregates in the case of Cu-Ni-Sn alloys. After ageing, their elongation is weak. Another example is the electrical conductivity which is very low in the case of the Cu-Ti alloys (<8%I.A.C.S). Therefore, to improve these performances, an optimization of the chemical compositions and of the thermal treatments proved to be necessary. To this end, four alloys have been kept first: the CuNi15Sn8, the CuNi6Si1.8Cr, the CuTi3Al2 and the CuTi3Sn2.75. The research started by a microstructural analysis of the segregation and extrusion states of these materials with the objective to assess the difficulties enable to be met during their processing. The second part dealt with the phenomena of precipitation during tempering and the relation mechanical/electrical properties and microstructure has been established in the light of current knowledges. The project has been reoriented then by the results on each of the reference alloys. Thus, the influence of the quaternary and quinary addition elements completed the survey of the CuNi15Sn8 alloy while the refinement of the major elements of the CuNi6Si1.8Cr alloys, CuTi3Al2 and CuTi3Sn2.75 has been privileged. Some alloys are proposed for a semi industrial validation and for an exhaustive characterization program.
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https://pastel.archives-ouvertes.fr/pastel-00667453
Contributor : Bibliothèque Mines Paristech <>
Submitted on : Tuesday, February 7, 2012 - 4:24:02 PM
Last modification on : Tuesday, October 20, 2020 - 11:22:54 AM
Long-term archiving on: : Wednesday, December 14, 2016 - 5:26:21 AM

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  • HAL Id : pastel-00667453, version 1

Citation

Valérie Lebreton. Étude métallurgique et optimisation de la fabrication d'alliages à base de cuivre coulés en continu : analyse de la ségrégation et des phénomènes de précipitation dans les alliages CuNi15Sn8, CuNi6Si1.8Cr, CuTi3Al2 et CuTi3Sn2.75. Matériaux. École Nationale Supérieure des Mines de Paris, 2007. Français. ⟨NNT : 2007ENMP1539⟩. ⟨pastel-00667453⟩

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