Teruo Takahashi1, Yasuhiko Hashimoto2 and Koichiro Koyama2
1Industrial Research Institute of Hyogo Prefecture, Kobe
The dilute Cu-Al binary alloys were internally oxidized in the temperature range of 973--1323 K, and the effects of Al concentration and internal oxidation temperature on the microstructure after internal oxidation were discussed. The results obtained are as follows.
Two anomalous microstructures made up of large oxide precipitates were produced depending on the Al concentration and internal oxidation temperature. One is a ``corn-like structure'' consisting of θ -Al2O3 and CuAlO2, which develops parallel to the diffusing direction of oxygen. Another is a ``wave-like structure'' consisting of α -Al2O3, which develops perpendicular to the diffusing direction of oxygen. For the alloys with solute concentrations of less than about 0.3%Al, there are no anomalous microstructures at the internal oxidation temperatures. In the range of 0.3-0.6%Al, only the corn-like structure develops. In the range of 0.6--1.4%Al, there are the areas of the corn-like structure or the wave-like structure and the coexisting area of both depending on the Al concentration and internal oxidation temperature, in which the corn-like structure spread into the area of high Al concentrations increasing with internal oxidation temperature. In the range of over 1.4%Al, there is only the wave-like structure at all the internal oxidation temperatures. The effects of Al concentration and internal oxidation temperature on the microstructure after internal oxidation was elucidated.
internal oxidation, copper-aluminum alloy, microstructure, oxide band, alpha alumina, theta alumina
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