Vacuum degassing behavior of rapidly solidified Al–Mn–Zr alloy powders

Gas desorption behavior and surface change characteristics of Al–Mn–Zr, Al–Mn, and Al–Zr alloy powders with heating in vacuo have been investigated by temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) measurements. TPD measurements on powders exposed to humid air, dry air, and high purity argon gas were performed to determine the gas species evolved during degassing of Al alloy powders. The alloy composition and P/M processing atmosphere had a strong influence on degassing behavior. The surface oxides of Al alloy powders containing Mn and/or Zr were prone to hydration. Thus, the formation of fresh Al2O3 on the Al alloy powders occurred at low temperature during vacuum degassing by the reaction, Al + 3H2O = Al2O3 + 3H2. High-temperature XPS showed that decomposition of the hydroxide into oxide on the Al–Mn–Zr alloys occurred at 623 K.