Peculiarities of Surface Interaction of Al+REM Alloys with Air and Water

The effect of the phase and chemical composition of aluminium+rare earth metal (1-2.5%R, ~22%R) polycrystalline alloys (Al+REM) on the rate of their surface film growth in air (at temperatures 400, 500, 600℃) and in water (~100℃) was studied. It is shown that in the temperature range 500-600℃ the oxidation of 1-2.5%R alloys in air is enhanced due to the increasing amount of REM oxide phases and crystallization of amorphous Al2O3. Al+1at.%Yb alloy shows the lowest oxidation stability in this temperature range owing to the formation of the greatest amount of REM oxides. Oxidation of Al+REM (~22%R) alloys in air begins at a temperature below 400℃. Their oxidation rate depends on the type and amount of dopant metal and the phase composition: the presence of REM-rich intermetallics in the alloy dramatically increases its reactivity. It is established that in the interaction of Al+REM alloys with boiling water, the active reacting phase is aluminum.