The formation kinetics of Cr₂O₃dispersed Cu synthesized by Cryo-milling

Abstract

Nano-crystalline (nc) Cu with Cr2O3 dispersoid (~4 vol.%) was successfully made by reactive-milling at 210 K with a mixture of pure Cu, Cu2O, and Cr powder. The vacuum hot pressing (HP) was performed at 1123 K and 50 MPa for 2h to consolidate the milled powder for further analysis. TEM (Transmission Electron Microscopy) work revealed that the HPed materials were comprised with a mixture of the nc-Cu and a homogeneous distribution of Cr2O3 dispersoids. The microstructure and Vickers hardness of the as-milled powder and the HPed materials were characterized by standard metallographic techniques. The grain size of the Cu was measured using Scherrer’s formula (XRD) and TEM observation; the Cr2O3 dispersoid size was estimated from the HADDF (High Angle Annular Dark Field) images and element mapping by STEM-EDS (Scanning Transmission Electron Microscopy-Energy Dispersive Spectroscopy) works. The formation kinetics and coarsening of the Cr2O3 dispersoids in Cu matrix were discussed based on the calculations with thermodynamic parameters in comparison with those of Al2O3.