Synergistic effect of Nb and Zr additions on the structure-property relationships of nanocrystalline Cu processed by mechanical alloying and hot pressing

In the present study, bulk nanocrystallineCu99.5Zr0.5, Cu99Nb1.0, and Cu98.5Zr0.5Nb1.0alloys have been synthesized by using mechanical alloying followed by hot pressing (HP) at 550 °C. Further, these as-fabricated alloys were annealed at 800 °C and 900 °C for 1 h to investigate the structure-property correlation. Grain size and phase identification has been carried out using X-ray diffraction (XRD) and transmission electron microscopy (TEM). While mechanical properties were investigated using Vickers hardness and shear punch test (SPT). The grain size of the as-processed alloys was found to remain nanosized 41 ± 2.2 nm in Cu99.5Zr0.5(CZ), 50 ± 1.5 nm in Cu99Nb1.0(CN) and 26 ± 1.2 nm in Cu98.5Zr0.5Nb1.0 (CNZ) even after annealing at 900 °C. This is attributed to the stabilization of the nanosize grains by segregation of solute atoms (Nb and Zr) along grain boundaries and/or Zenner pinning by intermetallic precipitates like Cu5Zr in CZ and CNZ alloys.