Comment on “Hardness based model for determining the kinetics of precipitation” by Mittra et al. [Mater. Sci. Eng. A 500 (2009) 244]

This paper describes the microstructures and nanomechanical properties of copper consolidated of oxidized submicron-sized Cu-powder (average particle size 410 nm) by spark plasma sintering (SPS). Good compact density, small grain size (460 nm) and microhardness of 1.24 GPa were achieved at 873 K in 6 min with 100 MPa, Cu2O-content being close to 20%. At higher sintering temperature, the grain size increased leading to decrease in hardness. The HIPed compact that was made for reference contained lower Cu2O and had lower density and larger grain size. It was concluded that the SPS process was superior to HIP consolidation in terms of microhardness and microstructure of the final material. Furthermore, the presence of Cu2O seemed not to have a marked effect on the SPS consolidation process, i.e. the obtained densities of the SPS samples were of 99.7% of theoretical density at the best.