Suzuki segregation in a binary Cu-Si alloy

Suzuki segregation to stacking faults and coherent twin boundaries has been investigated in a Cu-7.15 at.% Si alloy, heat-treatcd at temperatures of 275, 400 and 550degreesC, using field-emission gun transmission electron microscopy. Silicon enrichment was observed at the stacking fault plane and decreased monotonically with increasing annealing temperature. This increase in the concentration of solute at the fault is due to the stacking fault energy being lowered at higher values of the electron- to-atom ratio of the alloy. From a McLean isotherm, the binding energy for segregation was calculated to be -0.021 +/- 0.019 eV atom(-1). Hardly any segregation was observed to coherent twin boundaries in the same alloy. This is because a twin has a lower interfacial energy than a stacking fault, so that the driving force for segregation is diminished.