Synergistic effect of Nb and Zr addition in thermal stabilization of nano-crystalline Cu synthesized by ball milling

Present study concerns strengthening of nanocrystalline Cu-matrix by binary and ternary addition of Zr (0.5 at. %) and Nb (1.0 at. %) using ball milling at cryogenic temperature. Zr and Nb having low equilibrium solid solubility in Cu, thus powder blends were subjected non-equilibrium alloying. Mechanically alloyed samples were annealed at different temperatures (600-900 degrees C) for one hour. Stability of the nanocrystalline Cu-matrix even after annealing at 900 degrees C is attributed to the stabilization of nanocrystalline grains by segregation of larger solute atoms (Nb and Zr) along grain boundaries and/or Zener pinning by precipitates like Cu5Zr in Cu-Zr intermetallics.