DIVERSITY OF STACKING FAULT ENERGY DETERMINATIONS AND ITS SIGNIFICANCE

Observations have been made in pure Ag and dilute Ag-Zn alloys of the texture developed after 95% and 97.5% rolling reduction, of the X-ray faulting probability, α, and of the size of extended dislocation nodes. Comparison is made between values of the stacking fault energy, γ, inferred from these results and also with published data obtained using the τ3 technique. The most reliable results are believed to be those obtained with the node technique, which indicate a gradual decrease of γ with increase of solute content in the range 0-9.1 at.% Zn. Poor correlation between this finding and the results of the indirect techniques indicates that they are in some cases unsuitable for accurate determinations of the stacking fault energy. The very fact that poor correlation has been found indicates that the stacking fault energy is not the sole major factor in determining the mechanical properties of f.c.c. alloys. Nevertheless, all the techniques which have been employed are valuable when it is recognised that they are but partly dependent on γ and in addition sample over a wide range of stresses, and under static and dynamic conditions, the effects of dislocation interactions with lattice inhomogeneities. The degree of correlation between the X-ray faulting probability and node data has been examined in some detail, and the different dependencies of α-1 and γ on alloying in the Ag-Zn series indicate that extrapolation of a plot of α-1 normalised at one point to an established value of γ cannot be considered a reliable procedure. However, very similar differences in the variation of α-1 and γ in AgZn, AgIn and AgSn alloys suggest that a general extrapolation procedure may be devised to permit the determination of reasonable values of γ from measurements of α. © 1969.