Orientation dependence of elastic properties and internal stresses in sub-microcrystalline copper produced by equal channel angular pressing

The orientation characteristics of the elastic properties of sub-microcrystalline copper produced by equal channel angular pressing (ECAP) were studied by measuring the velocities of the longitudinal and transverse ultrasonic waves in different spatial directions. It was shown that the effect of an 'anomalous' reduction in the elastic moduli observed after ECAP treatment reflects a strong spatial anisotropy of the material. Internal stresses arising in copper as a result of ECAP processing were determined by means of X-ray diffraction line broadening analysis. An appreciable anisotropy of the internal stresses was also found. Possible mechanisms responsible for the anomalies of the elastic properties are discussed.