X-ray diffraction analysis of thermal behavior of nanocrystalline copper produced by severe plastic deformation

X-ray diffraction analysis carried out at 85-295 K was used to study nanocr ystalline copper of 93.98% purity produced by seven plastic deformation. Da ta obtained for copper produced by severe plastic deformation by torsion an d equichannel angular extrusion were analyzed within the quasi-harmonic Deb ye approximation. The analysis showed the decrease in the Dehye temperature (19-23%), increase in static (similar to 45%) and dynamic (similar to 48%) atomic displacements, and increase in the coefficient of linear thermal ex pansion (more than 3 times) as against those for coarse-grained copper. The decrease in the Debye temperature is likely to be due to the formation of nonequilibrium grain boundaries. The results agree with the data on the You ng's and shear adiabatic modules obtained earlier by the ultrasonic techniq ue.