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Various Al-Cu alloy powder particles were produced by electrohydrodynamic atomization. The particles produced by this process range in size from 3 nm to 2 μm. The microstructure of the submicrometre particles is shown, and a discussion of their cooling rates and solidification history is presented.
The alloys produced included various compositions of aluminum and copper. Extended solid solubility was observed in all the alloys and was dependent on the particle size and concentration. The particles produced from alloy concentrations beyond the equilibrium solubility limit which exhibit segregation-free microstructure probably solidified after undercooling sufficiently to produce the interfacial temperatures and velocities necessary to suppress segregated growth. These aspects of solidification are discussed and estimates of the cooling rates and bulk undercoolings achieved are given. Some of the particles show a transition from partitionless solidification to a segregated, cellular solidification.
aluminum alloys, powder metallurgy, submicrometre particles, aluminum-copper alloys, microstructure, solidification, supercooling
Metallurgist, Metallurgy Division, National Bureau of Standards, Gaithersburg, MD
Research associate, Center for Materials Research, Johns Hopkins University, Baltimore, MD