Abstract
The phase composition and structure of initial powders and the products of oxidation of aluminum alloys with calcium and barium containing 0.88 and 0.26 at.% of dopants, respectively, have been studied for the first time by the diffraction method with the use of synchrotron radiation during programmed heating in air up to 1273 K at a rate of 10 K/min. It was established that as a result of the heterogeneity of the phase composition of the oxidation products and the structural changes in the oxide shell on the particle surface, aluminum oxide loses its high protective properties and metal oxidation is activated.
Highlights
Analysis of the physicochemical properties of aluminum-based alloys and the experimental data on their oxidation during programmed heating showed that structure heterogeneity of the metal core of the powders and the products of interaction on the surface contributes to the discontinuity of the barrier layer and increases the reactivity [1]
High segregation of Ca and Ba in the surface layers of aluminum-based alloy powders was established by XPS [2, 3]
Based on the results of these studies it was suggested that calcium and barium concentrate on the particle surface in the form of intermetallic compounds corresponding to aluminum-richest compositions (Al4Ca, Al4Ba) on the phase diagrams of the investigated binary systems
Summary
Analysis of the physicochemical properties of aluminum-based alloys and the experimental data on their oxidation during programmed heating showed that structure heterogeneity of the metal core of the powders and the products of interaction on the surface contributes to the discontinuity of the barrier layer and increases the reactivity [1]. Based on the results of these studies it was suggested that calcium and barium concentrate on the particle surface in the form of intermetallic compounds corresponding to aluminum-richest compositions (Al4Ca, Al4Ba) on the phase diagrams of the investigated binary systems. When the alloys transform into liquid state, the particle surface is enriched with a surface-active additive, which is present there in the structure of ordered microgroups corresponding to the most stable intermetallics, as shown in [4]. In this work we studied experimentally the physical and chemical processes occurring during oxidation of aluminum-based powders doped with Ca and Ba in air
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