Changes in the Surface Characteristics of Gas-Atomized Pure Aluminum Powder during Vacuum Degassing

Abstract

Vacuum degassing is essential in the preparation of RS P/M aluminum alloys to remove adsorbates and for the decomposition of hydrated-Al₂O₃ on the powder surface. Changes in the surface characteristics during vacuum degassing were investigated by X-ray photoelectron spectroscopy and temperature-programmed desorption measurement. Hydrated-Al₂O₃ decomposition to crystalline-Al₂O₃ and hydrogen desorption on the surface of argon gas-atomized aluminum powder occurred at 623 K and 725 K, respectively. This temperature difference suggests that the reaction converting hydrated-Al₂O₃ to crystalline-Al₂O₃ during vacuum degassing should be divided into the two reactions “2Al+Al₂O₃·3H₂O→2Al₂O₃+6H_surf” and “6H_surf→3H₂”.