Internal Friction and Critical Stress of Copper Alloys

Abstract

The effects of strain amplitude on the internal friction and the Young's modulus of polycrystalline specimens of copper alloys (Cu–Zn, Cu–Al, Cu–P) with various concentrations of solute atoms have been investigated. The results are: 1. The critical stress, up to which the internal friction and the Young's modulus are almost independent of strain amplitude, increases with concentration of solute atoms, showing a considerable harmony with the theoretical stress obtained by Mott. 2. The strain-independent part of the internal friction decreases as a power function of concentration of solute atoms, although its numerical value depends largely on the pre-treatment. 3. The strain-dependent part of the internal friction and the fractional change of Young's modulus are represented by two parallel fomulae, as in the theory of Nowick. But the factors of strain-dependencies seem to increase with concentration of solute atoms. 4. The internal friction and the Young's modulus are both almost independent of frequency in the range between 900 and 10,000 cps at at room temperatures.