Nonlinear acoustic response from precipitate-matrix misfit in a dislocation network

An analytical model is presented for the effects on the acoustic nonlinearity of the interaction of matrix dislocations with precipitate coherency strains in metallic alloys. The acoustic nonlinearity parameters are shown to depend linearly on the dislocation density, volume fraction of precipitates and precipitate-matrix misfit parameters, and on the fourth power of the dislocation loop length. The model predicts changes in the acoustic nonlinearity parameter associated with the growth of precipitates during the artificial aging of aluminum alloy 2024 that are in good agreement with experimental measurements reported in the literature. [S0021-8979(98)04222-4].