Influence of ageing process on sound velocity in C17200 copper–beryllium alloy

This paper has been aimed to explore the influence of ageing process on sound velocity in C17200 copper–beryllium alloy. It was shown that the variation of sound velocity with ageing time follows a two-stage regime, the first stage with a sharp decreasing trend and the second stage developing with an almost constant velocity. Electrical conductivity measurement was applied to provide quantitative evidences to determine the governing mechanism in each stage. It was revealed that the origin of the first stage is the segregation of solute atoms from the matrix, regardless of the ageing temperature. The origin of the second stage, however, was dependent on the ageing temperature. For ageing temperature of 315 °C, increased contribution of the coherent precipitates to the overall elastic modulus of the material was known as the governing factor, and for ageing temperature of 380 °C significant formation of γ equilibrium precipitates was introduced as the responsible factor. Also, it was observed that the correlation between sound velocity and strength of the alloy changes with increase of ageing temperature.