Abstract
Precipitation processes of a Cu-Zr-Cr ternary alloy have been investigated by means of specific heat and electric resistance measurements, comparing with those of Cu-Zr and Cu-Cr binary alloys. Specimens were solution-treated at 950°C and quenched into iced water. Subsequently they were aged or cold-rolled about 83% and then aged under various conditions. In this study, the precipitation processes during aging at temperatures elevated at a constant rate of 2°C/min were examined in detail. The results obtained were as follows: (1) In the as-quenched specimen, Cr precipitate appeared first at about 440°C and then Cu3Zr precipitate occurred separately at about 520°C. The former temperature was about 15°C higher than that of Cu-Cr alloy. In the worked specimen, the order of precipitation was reversed, that is, Cu3Zr and Cr appeared at about 370°C and 425°C, respectively. (2) The two sorts of precipitation temperature observed in each case of the ternary alloy agreed well with that of each binary alloy, with the exception of the above-mentioned temperature of Cr precipitates. (3) It was shown that the above results could satisfactorily be explained by the precipitation diagram (the T-T-T diagram) of the ternary alloy which was established qualitatively as consisting of four curves (two curves corresponding to homogeneous and heterogeneous precipitations of Cr and the other two curves of Cu3Zr). The property changes during isothermal aging can also be accounted for by using this diagram.
