Anomaly of Specific Heat in α-Phase Alloys of Copper and Aluminium

The specific heats of 12 copper alloys containing less than 14.59 per cent of aluminium were measured at high temperatures at annealed and baked states by the inverse rate curve method. In the case of the α-phase alloy containing more than 3.98 per cent of aluminium, the specific heat-temperature curve shows, in an annealed state, a small maximum at the temperature about 340 to 300° ; the temperature lowers with the increase of aluminium content and the anomaly is most conspicuous in the alloys containing 8.05 or 9.14 per cent of aluminium. The anomaly is also observable in alloys in the mixture range ; in the specific heat curve of these alloys, another maximum is observed at about 400°, the origin of which was uncertain. When the alloys are heated at 210°for 200 hours, the anomaly in the α-phase becomes very large, and the temperature of the maximum is almost constant (about 305°). The anomaly observed at high temperature is considered to be caused by the formation of a superlattice of short range order Cu_3Al