Segregation of calcium on the surface of aluminum-based powders and its effect on oxidation kinetics

Segregation in the surface layers of an aluminum alloy powder containing 1.3 wt % calcium is studied. With the use of X-ray photoelectron spectroscopy, it is found that the surface calcium content is increased to 34 wt % compared to the bulk. Oxidation of the powder in air studied with the use of thermogravimetry and differential scanning calorimetry showed that the high surface concentration and high chemical activity of calcium result in a doubling of the reaction yield at a temperature of 1750 K.