Abstract
The breakaway oxidation, mainly at 850°C, of 2.5% tin-zirconium alloy in oxygen has been investigated by thermogravimetric measurement, electron microscopic observation, electron-probe microanalysis and X-ray diffraction analysis. In the post-breakaway stage, the oxidation kinetics was remarkably affected by the pressure of oxygen, and severe cracking of the oxide film was observed. The electron-probe microanalysis and X-ray diffraction analyses indicated that the tin in the alloy was precipitated as an intermetallic compound of ZrSn at the oxide/metal interface, and suggested that the oxide film has a multilayer structre consisting of ZrO2 and (ZrSn)O2 layers. The mechanism of the pronounced breakaway phenomenon of tin-zirconium alloy was discussed on the basis of the behavior of tin in the alloy, and it was concluded that stress between the layers of ZrO2 and (ZrSn)O2 induced the cracking of the oxide film and permitted the increased oxidation.
