Sensitivity of ultrasonic attenuation and velocity change to cyclic deformation in pure aluminum

The average dislocation density Λ and loop length L in cyclically deforming Al were derived from the measurement of ultrasonic attenuation and velocity change. With the increase of the cycle number, Λ increases at first and then decreases a little after passing a maximum, while L decreases monotonously. At low cyclic strain amplitudes less than 10-4, Λ and L almost do not change with cycle number. These results show that the measurement of ultrasonic attenuation and velocity change is a useful method to determine the parameters Λ and L in the process of cyclic deformation.