Abstract
In the rapidly solidified powder metallurgy processing of aluminum alloys, vacuum degassing is one of the important process steps. The aim of the degassing is removing the adsorbed gaseous species from powder surface, and transforming the ductile hydrated alumina and aluminum hydroxide into brittle g-alumina in order to realize the formation of metal- to-metal bonding between powder particles during consolidation. Temperature-programmed desorption measurement on powders exposed to humid air, dry air and pure argon gas was performed to determine the gas species evolved during degassing for powders of Al-Ti-Fe-Cr and Al-Zn-Mg-Cu-Ag alloys. The surface composition and processing atmosphere significantly influenced degassing behavior of the powders. The su rface oxide of Al- Zn-Mg-Cu-Ag powder was more prone to hydration than that of Al- Ti-Fe-Cr powder. Accordingly, the formation of fresh Al2O3 on the Al-Zn-Mg-Cu-Ag powder occurred at low temperature during vacuum degassing by the reaction, Al + 3H2O = Al2O3 + 3H2.
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