Structural characterization of nanocrystalline copper by means of x-ray diffraction

Quantitative x-ray-diffraction measurements were performed on a nanocrystalline Cu sample made by severe plastic deformation. The shape of Bragg reflections was found to be represented primarily by a Lorentzian function. A difference of as much as 6%±3% was revealed between the integrated intensities from the nanocrystalline and a reference coarse-grained Cu samples. The broadening of Bragg reflections from the nanocrystalline Cu sample was mainly induced by small crystallite sizes and microstrains inside the grains and/or the deformed layers near the grain boundaries. It was found that the grain sizes of nanocrystalline Cu in different crystallographic orientations are essentially the same, while the microstrains exhibit a significant anisotropy. The Debye–Waller parameter B of the nanocrystalline Cu sample was 0.97±0.06 Å2, which suggests that the atomic displacement from their ideal lattice positions equals on average 0.111±0.004 Å or 4.3% of the nearest-neighbor spacing.