Formation of the L12-type superstructure in Cu-5.9 at.%Pd and Cu-8 at%Pd alloys

There was performed a resistometric study of the Cu-8 at.%Pd alloy during heating and cooling with a constant rate. There was made a comparison with the change in the electrical properties of the Cu-5.9 at.%Pd alloy. In the investigated Cu-Pd alloys, the anomalous behavior of electrical properties was revealed: long low-temperature annealing increased the electrical resistivity. It was concluded that nuclei of the ordered L12 phase were formed in the Cu-5.9 at.% Pd alloy. The obtained result is in contradiction with the currently known Cu-Pd phase diagram, where the Cu-5.9Pd alloy is the fcc-solid solution. The critical temperatures of the order→disorder phase transformation in the alloys were determined.