Hybrid thermal stabilization of Zr doped nanocrystalline Cu

Abstract

The present investigation demonstrates the synthesis of nanocrystalline Cu-0.5 at.% Zr alloy through high energy ball milling at cryogenic temperature and thermal stability of the nanocrystalline structure during annealing up to 800 °C. The effect of Zr addition on the evolution of microstructure in the cryomilled and annealed alloy has been studied through X-ray diffraction (XRD), transmission electron microscopy (TEM), and Molecular dynamics (MD) simulation. Microhardness measurement has been performed in order to study the stability in the mechanical property of the alloy at high temperature. Analysis of XRD and TEM results show that at high-temperature Zr leaves Cu matrix and nano-size intermetallicCu5Zr particle dispersed throughout the matrix, whereas, MD simulation traced atomic clusters of Zr at the vicinity of grain boundaries. Zr stabilizes the average grain size in nanoscale regime even after 800 °C due to intermetallic pinning and solute segregation, with very little compromise in the hardness value of only ~7.4% (2.9 GPa to 2.4 GPa) compared to the as-milled alloy. Keywords: Nanocrystalline, Grain growth, Segregation, Pinning, Thermal stabilization