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6591 |
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Heat treatment of high strength aluminum powders for enhanced cold spray deposition |
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Luke Brewer* / The University of Alabama, USA Arthur Webb / The University of Alabama, USA William Story/ The University of Alabama, USA Tian Liu/ The University of Alabama, USA Brian Jordon/ The University of Alabama, USA |
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This presentation will describe new results on the heat treatment of AA2024 and AA7075 feedstock powder for cold spray deposition. Cold spray deposition is being developed as a means for repairing corrosion damage in high strength aluminum aircraft components. The microstructure of gas atomized powders is not optimized for spray characteristics or for mechanical properties. We have applied a new heat treatment approach to solutionize these powders, thus removing the intermetallic network that forms during rapid solidification. Inert gas atomized powders of AA2024, AA6061, AA7050, and AA7075 were solutionized over a range of temperatures from 450-500°C in a novel rotary furnace and then quenched while in an inert atmosphere. All of these powders were cold sprayed onto substrates of their own same composition using the VRC Metal Systems generation III cold spray system with helium as the spray gas. The mass deposition efficiency for all solutionized powders improved significantly with an increase of 25% for the AA7075 powder and a 63% increase for the AA2024 powder. Detailed materials characterization, including optical microscopy, electron microscopy, and x-ray diffraction is being used to show how the micro- and nanostructures of the feedstock powders are changed by the powder heat treatment and by the cold spray process. For example, solution heat treatment of AA2024 powders removed the majority of the S phase intermetallics from the feedstock powder. After cold spray of this material, transmission electron microscopy showed the formation of nanoscale S phase in the deposited material. Similar results will be presented on AA7075 feedstock powder and deposited coatings. |