Structural studies of submicrocrystalline copper and copper composites by different methods

摘要

Microstructure of Cu, Cu + Al_2O_3, Cu + Zr samples deformed by high pressure torsion and equal channel angular pressing was studied by several methods: X-ray diffraction (XRD), transmission electron microscopy (TEM), positron annihilation spectroscopy (PAS) and electron back-scatter diffraction (EBSD). Line broadening analysis showed that the HPT samples have smaller crystallite size compared to the ECAP samples while the dislocation densities were similar – of the order of 1 x 10~(15)m~(-2). Only small changes in the mean dislocation density with increasing number of ECAP passes were found by XRD. On the other hand, significant microstructural changes and grain fragmentation were revealed by TEM and EBSD. With increasing strain due to ECAP elongated dislocation cells with low-angle boundaries developed into more equiaxed subgrains and grains separated by high-angle grain boundaries.