INFLUENCE OF SOLUTE ATOMS ON THE STACKING FAULT ENERGY IN alpha Cu-Al ALLOYS.

Abstract

Extended dislocation nodes in alpha Cu-Al solid solution were observed by transmission electron microscopy. For determinations of the stacking fault energy (SFE) as a function of composition, the specimens were annealed at 700 degree C after deformation to eliminate the effect of solute impedance force pinning partial dislocations. Differences between the results obtained and literature data are attributed to solute impedance stress. A Cu-15. 9at. %Al alloy, quenched from different temperatures, was used to study the effect of short range order (SRO) on the SFE. The results suggest that SRO is not only responsible for the frictional effects, as suggested by many workers, but also might affect the true SFE. The SFE decreases with development of SRO in the sample where stacking faults already exist. This effect of SRO is in the opposite sense to that found when the stacking faults are introduced in an ordered alloy.