Diffusion of 63ni in Severely Deformed Ultrafine Grained Cu-based Alloys

Cu-Hf and Cu-Cr-Hf alloys have been subjected to severe plastic deformation applying equal channel angular pressing and high pressure torsion. Grain boundary diffusion was measured in a temperature interval between 423K and 570K using the radiotracer technique with the 63Ni isotope as tracer. The microstructure evolution examination using scanning electron microscopy showed no structural changes during diffusion annealing. Diffusion profiles in pressed samples reveal the occurrence of a percolating porosity, whereas no such porosity could be detected in the twisted samples. The determined diffusion coefficients correspond to those in severely plastically deformed Cu alloyed with Pb or Zr.