The effect of external stress on discontinuous precipitation has been investigated. The driving force for discontinuous precipitation under external stress depends on the inherent coherency strain and external stress. The prediction of the driving force for discontinuous precipitation in terms of coherency strain model and elastic theory has been tested in Cu-Ag-Co alloys.
In Cu-3.22at.%Ag alloy where the coherency strain is tensile, the preferred direction of cell growth was perpendicular to the direction of the applied tension, whereas in Cu-0.79at.%Ag-2.06at.%Co alloy where the coherency strain is compressive, it coincided with that of the applied tension. The directionality was the more evident the higher the tension. The discontinuous precipitation did not occur regardless of applied external tension in Cu-1.91at.%Ag-1.21at.%Co alloy where the coherency strain energy is approximately zero. All of this results are consistent with the prediction based on the coherency strain model.
