Compressive yield strength of the nanocrystalline Cu with Al2O3 dispersoid

Nanocrystalline (nc) Cu with Al2O3 dispersoid (similar to 4 vol.%) was successfully synthesized by simple cryomilling at 210K with a mixture of Cu2O, Al, and Cu elemental powders. The milled powder was consolidated by hot pressing (HP) at 1123K and 50 MPa for 2 h. TEM (Transmission Electron Microscopy) work revealed that both of the milled powder and the hot pressed (HPed) materials were comprised with a mixture of the nc-Cu and homogeneous distribution of Al2O3 dispersoids. The compressive and micro Vickers hardness tests were performed on the HPed materials (nanocrystalline Cu with 4 vol.% of Al2O3 dispersoid) at room temperature to characterize the mechanical properties of the materials. The compressive yield strength of the materials was as high as 863 MPa; the micro Vickers hardness 2600 MPa. The results of the mechanical tests apparently show that the relationship between the yield strength and the micro hardness of the HPed materials is in well agreement with Tabor's rule, H-v = 3 sigma(y) in MPa. The grain size of the nc-Cu was estimated by XRD using Scherrer's formula and TEM observation; the Al2O3 dispersoid size was measured from element mapping by STEM-EDS (Scanning Transmission Electron Microscopy-Energy Dispersive Spectroscopy) works. An attempt was made to quantify the possible strengthening effects of the nc-Cu materials with Al2O3 dispersoid. Two strengthening mechanisms were proposed for high hardness and yield strength of the materials, i.e., grain size and dispersion hardening effects. (C) 2010 Elsevier B.V. All rights reserved.