Copper alloys have been used for plain bearing material in many kinds of engineering machines. In this study typical copper alloys are selected from the view point of strength and thermal conductivity that is proportional to electric conductivity. The aim of this study is to investigate that the thermal conductivity is very important character to keep mild friction with appropriate condition of block-on-ring tests. The results show that the patterns of friction coefficient of time are classified into four types. Type I is stable in low friction. Type II is slightly up in the end part. Type III is less stable and up to 0.4 level of friction coefficient (μ). Type IV is rough waving in more over 0.4 level of friction coefficient (μ). The materials of Type I are chromium copper alloy and Corson copper alloy. The Type II is beryllium copper alloy. These Type I & II alloys have the same properties of high thermal conductivity and characteristic microstructure of dispersed hard particles in copper matrix. High thermal conductivity reveals good tribological performance, i. e., low friction and wear. Moreover after tribological test, the surface of these alloys changes and transformes to rich oxide surface with condensed hard particles. It's action is simple application of friction steps to escape the severe wear. Especially the copper alloy with ferrous particles dispersed in matrix makes severe mode of friction by the same element of friction.

The influences of solution treatments, prior cold drawings and aging treatments on mechanical properties in Corson alloy with high contents more than 8.0 mass% of Ni and Si have been investigated. As a result of the optimization of conditions, the maximum hardness and tensile strength reached 306HV and 968MPa, respectively. Effects of temperatures of solution treatment and aging on the mechanical properties were analyzed based on solid solute concentrations in matrix phase, which were estimated by using the linear analysis and calculated from the electrical conductivity. The solute concentrations were also measured directly by SEM-EDS. Consequently, the precipitation hardening of the alloys was governed mainly by the solute concentrations of Ni and Si in matrix phase in solution treatment. The hardness depended on not only the solute concentrations but also the excess of Ni and Si in the alloys.

EVWUDFWEffect of Ag content on grain growth during reversion in precipitation hardened Cu-Cr-Zr-Ag alloys has been studied. Changes in grain size and electrical conductivity during annealing at 900°C were investigated in the different Ag content alloys. Grain growth exponents n were derived from relation between annealing time and grain growth rate. For annealing time ranged from 500 s to 21.6 ks, the minimum grain growth exponent n of 0.09 was found in the alloy including Ag of 0.27 mass%. Effect of Ag addition on electrical conductivity for annealed alloys were analyzed according to the corrected Nordheim's Rule, in which the calculated conductivity from binary phase diagrams Cu-Cr, Cu-Zr and Cu-Ag was higher than the practical value. These results suggested that Ag was effectively added to Cu-Cr-Zr ternary alloy to suppress grain growth of D phase in holding at elevated temperature and to increase solubility of Cr at 900°C in matrix.

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