Development of High Strength-High Conductivity Cu-6 wt% Ag Alloy for High Field Magnet
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Development of High Strength-High Conductivity Cu-6 wt% Ag Alloy for High Field Magnet
Yoshikazu Sakai 1, Takaaki Hibaru 2, Kiyoshi Miura 3, Akira Matsuo 1, Koushi Kawaguchi 1 and Koichi Kindo 1
1
The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba, Japan
2
National Institute for Materials Science, Tsukuba, Ibaraki, Japan
3
Showa Cable Systems Co., Ltd., Sagamihara, Kanagawa, Japan
ABSTRACT One of the authors developed the high strength and high conductivity Cu-24 wt% Ag alloy as a conductor material for high field magnets twenty years ago. Wire and sheet of the alloy have been used as a conductor material for pulsed magnets or resistive magnets of the high magnetic field facilities of each country. However, the alloy required large quantities of Ag addition to achieve high strength. The cost performance and workability of the alloy were not good for that. So, we investigated possibility of low Cu-Ag alloy for decreasing in material cost and improving in workability. We succeeded in the development of the Cu-6 wt% Ag alloy by the new heat treatment which is superior to the characteristic of the Cu-24 wt% Ag alloy even if the amount of Ag content is decreased in 1/4. At present, we make a lot of high field pulsed magnets by using the Cu-6 wt% Ag wire manufactured industrially, and do that magnetic field experiment and are getting good results at the ISSP, the university of Tokyo. We will talk about the characteristic, new heat treatment method and the manufacturing process of the conductor material for the Cu-6 wt% Ag alloy. INTRODUCTION Conductor materials for high field magnets such as pulsed magnets and resistive magnets must have both high strength and high electrical conductivity to stand the strong Lorentz force and to reduce Joule heating. However, relationship between strength and conductivity of Cu based alloys is trade off. Cu-Be alloys have high strength but conductivity is low. On the other hand Cu-Cr, Cu-Zr, Cu-Al2O3 alloys and pure Cu have high conductivity but strength is low. Cu-Nb alloy and Cu-Ag alloy have both high strength and high conductivity among others. At present, Cu-Nb alloy and Cu-Ag alloy are being used as a conductor material of the high field magnet. These alloys called metal matrix composites (MMCs) have both high strength and high conductivity compared with conventional Cu alloys [1-5]. The Cu-24 wt% Ag alloy achieved strength of 1 GPa and conductivity of 80 %IACS [6]. The Cu-24 wt% Ag alloy consists of two phases, namely Cu rich phase and Ag rich phase [7]. These two phases are compressed and
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extended by plastic working such as wire drawing and rolling, finally becomes ultrafine fiberlike structure. The ultrafine fiberlike structure realizes higher strength than 1 GPa. Besides, Cu-Ag alloy keeps high conductivi
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