GRAIN STABILIZATION OF COPPER WITH NANOSCALED AL2O3-POWDER

Copper powders with a median particle diameter of 60 mu m were mixed w ith different amounts of nanosized alumina powder with a median partic le diameter of 14 nm in an asymmetric moved mixer followed by hot extr usion. Investigations of the microstructure reveal considerable less r ecrystallization and grain growth up to temperatures near to the melti ng point of copper, compared to hot extruded samples made of copper po wder without additives and composites with microsized alumina powder c ontent. It was shown by EDX measurements, that the nanosized alumina p articles are located exclusively at the grain boundaries of the copper grains. Due to the nanopowder additions an increase in hardness and y ield stress is observed, which can be attributed to inhibited recrysta llization and grain growth. (C) 1997 Elsevier Science S.A.