Contribution of dislocation evolution to acoustic nonlinearity in plastically damaged materials

In order to investigate the relationship between nonlinear ultrasonic signals and microstructure changes of plastically deformed materials. In this work, three sets of pure Cu were annealed for one hour at 350 °C 650 °C, 750 °C (isochronously annealed), respectively, to produce grains with different sizes inside Cu. These heat treated samples were underwent interrupted uni-axial tensile tests to get different plastic strains. Ultrasonic measurements were carried out to introduce controlled levels of plastic strain to determine the nonlinear response of longitudinal wave. Finally, the micro-structure evolution observed by transmission electron microscopy (TEM) and electron back scatter diffraction (EBSD) was analyzed to understand its contribution to the acoustic nonlinearity in the plastically damaged Cu.