Effect of Ag Content on Electrical Conductivity and Tensile Properties of Cu-Ti-Ag Alloys
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Effect of Ag Content on Electrical Conductivity and Tensile Properties of Cu-Ti-Ag Alloys Taek-Kyun Jung1, Dong-Woo Joh1, Hyo-Soo Lee1 and Hyuk-Chon Kwon1 Korea Institute of Industrial Technology, 7-47 Songdo-dong, Yeonsu-gu, Incheon 406-840, Korea.
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ABSTRACT Effects of Ag content on microstructure, mechanical properties, and electrical conductivity in long time aged Cu-Ti-Ag alloys were investigated. In short time ageing condition, both electrical conductivity and mechanical properties were enhanced by Ag addition. On the other hand, in long time ageing condition, Ag addition showed a faster deterioration of mechanical properties than Ag free CuTi alloys. INTRODUCTION Copper and copper alloys are widely used for numerous industrial fields requiring high mechanical properties, high electrical conductivity and resistance to corrosion [1-2]. Among the several copper alloys, Cu-Be based alloys are used as materials for electrical or electronic components, welding parts, spring, switch and relay parts because of their high strength levels, good electrical conductivity, resistance to corrosion, and good wear property. However, Cu-Be alloys have a relative high production cost and result in serious problems such as a potential health hazards by Be fumes during melting, grinding, machining, and welding. In order to solve these problems, several Cu alloys (Cu-Cr, Cu-Zr, Cu-Ti) have been developed as alternative materials, Cu-Ti alloys are recently attractive as a candidate among them [2-4]. It has been reported that tensile strength of higher 1GPa and electrical conductivity of about 15%IACS could be achieved by precipitation hardening, fine grain size, and high dislocation density in terms of solution treatment, cold working, and ageing treatment. S. Nagarjuna et al. reported that strength in solution treated Cu-Ti alloys increase linearly up to 4wt%Ti and show a sharp increase with further additions of Ti, due to fine scale precipitation in the form of modulations in Cu-4.5wt%Ti alloy [5]. However, since electrical resistivity per 1wt% Ti addition in Cu is very high (21.6ȝȍ·cm) and solubility of Ti in Cu is 0.4wt% at 293K, electrical conductivity of Cu-Ti alloys is lower than other precipitation strengthened Cu alloys even after ageing treatment. Recently, Semboshi et al. reported that electrical conductivity of Cu-Ti alloys is more improved by ageing in H2 atmosphere than in Vacuum atmosphere at long time ageing [1, 6]. They found that finely dispersed precipitates of Į-Cu4Ti were formed in a similar manner to ageing in a vacuum but particles of titanium hydride, į-TiH2 were formed by further ageing in H2 atmosphere. High electrical conductivity of Cu-Ti alloys aged in H2 atmosphere is related to the precipitation of titanium hydride resulting in a decrease of residual Ti concentration in Cu matrix. However, a long time ageing in both vacuum and H2 atmosphere also results in a decrease of mechanical properties by a coarsening of the Į-Cu4Ti precipitates. In this work, we tried to investigate an effect of third element
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