In the previous report, the authors tried to obtain the T/T/T-diagrams for two kinds of Cu-Al binary alloys containing 11.44 wt% and 12.18 wt%Al respectively. And it was found that some complex phenomena occurred with the decomposition of the β phase at the temperature below the eutectoid temperature. In consideration of the results of this experiment, the following processes may be deemed reasonable. When
Th>
Tc, β→α or γ
2+
E and when
Th<
Tc, β→β
1+α→
E+α.
Th and
Tc stand for the temperature of holding and the critical temperature of β→β
1, respectively. It has been shown that the transformation β→β
1 preferentially proceeds at the temperature below
Tc, and some characteristic structures, the so-called rosettes or granular precipitates and sheaths enveloping α have appeared with the formation of β
1. Now, to confirm these phenomena again, the authors have carried out some experiments for obtaining the T/T/T-diagrams for the specimens of 12.49 wt%, near the ideal Cu
3Al composition, and of 12.96 wt%Al content. From the present experimental results, it was found that the transformation β→β
1 predominantly proceeds at the temperature below
Tc causes the alteration of Al concentration, and then the eutectoidal decomposition occurs directly from the β phase of the alloy containing 12.49 wt%Al. Some discussions about the mechanism of the transformation β→β
1 in Cu-Al binary alloys are appended.
抄録全体を表示