Heterogeneous microstructure of an Al2O3 dispersion strengthened Cu by spark plasma sintering and extrusion and its effect on tensile properties and electrical conductivity

Introducing coarse grains into nanocrystalline (NC) and ultrafine grained (UFG) metallic materials can lead to an excellent combination of strength and ductility. In this study, we produced Al2O3 dispersion-strengthened (Al2O3-DS) Cu with heterogeneous microstructure by mechanical alloying (MA) of Cu-Al2O3 powder mixture followed by spark plasma sintering (SPS) and hot extrusion (HE). For direct comparison, one sample was prepared by hot extrusion only without prior SPS of mechanically alloyed (MAed) powders. The microstructure of materials produced via a combination of SPS and HE possessed the heterogeneous microstructure consisting of Al2O3-free coarse grained (CG) Cu bands and Al2O3-rich UFG Cu regions. These different microstructural regions were found to play different roles on the tensile and electrical properties and their presence can be tuned to achieve desired mechanical and electrical properties. We also discuss the possible mechanisms responsible for the formation of the heterogeneous microstructure in the samples produced by a combined process of SPS and HE.