Mechanical properties and thermal stability of bulk Cu cold consolidated from atomized powders by high-pressure torsion

It is difficult to densify and consolidate round-shaped metallic powders by conventional compaction techniques because powder interlocking forces are small and the powders easily slip and rotate instead of being plastically deformed and densified. In this paper, atomized Cu (99.5 % purity) powders of round shapes were cold consolidated to bulk specimens by high-pressure torsion (HPT) under 10 GPa to avoid powder slippage by the shape effect. A relative density over 98 %, high tensile strengths of 642 and 570 MPa, and moderate ductility of 7.5 % with thermally stable ultrafine grained structures are achieved after the HPT consolidation process. The specimens HPT processed at RT show higher tensile strength due to more dislocations and finer grain sizes than the specimen processed at 373 K. Higher ductility in the elevated temperature (373 K)-processed specimen than in the RT-processed specimen is attributed to good bonding between particles, decreased dislocation density, and increased grain size.