Tadashi Igarashi1, Masahiro Shibata1 and Mitsuo Osada1
1R & D Group, Sumitomo Electric Industries, Ltd., Itami
Ag-Cd and Ag-Cd-Sn alloys containing 10∼17 mass%Cd and 0.5∼1.5 mass%Sn were oxidized at 973 and 1073 K under oxygen pressures of 2.1×104 and 1.0×105 Pa in order to investigate the precipitation behavior of oxides during internal oxidation. Microstructures, distribution of Cd and Sn in oxides, and oxide phases were investigated by optical microscopy, electron probe X-ray microanalysis, and X-ray diffraction, respectively. Oxidation tendency of solute elements were estimated with an EPMA, by utilizing oxide enrichment produced at the oxidation front when oxidation conditions were changed rapidly to higher temperature and lower oxygen pressure.
The results obtained are as follows:
(1) Massive oxides in Ag-Cd alloys were changed into fine needle-like oxides by addition of Sn. The most remarkable effect was obtained with 0.5%Sn.
(2) Oxide phases precipitating at 973 K were identified as CdO, Cd2SnO4, and CdSnO3. CdO and Cd2SnO4 precipitated at 1073 K.
(3) SnO2 or composite oxides of CdO and SnO2 precipitated followed by precipitation of CdO on the oxides. It was considered that SnO2 converted into composite oxides by reaction with CdO.
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