Diffraction Contrast from Dissociated Frank Dislocations. II. Comparison of Experimental and Computed Electron Micrographs

Abstract

SummaryExperimental and computed images for edges of Frank dislocation loops in quenched copper-aluminium alloys and in quenched silver are compared. The comparison shows that Frank dislocations are dissociated in these materials. By matching the computed and experimental images, the degree of dissociation is determined and the stacking fault energy of the various materials is estimated.

Precipitate assemblies formed on dislocation loops in aluminium-silver alloys

“…Hardness measurements Hardness curves obtained from Vickers hardness tests on the binary alloys are shown in Figure 1 , however there is no reversal of the dislocation line strain contrast (indicated with hollow arrows). The latter feature is characteristic of a dissociated Frank loop [12,13]. The presence of the fine-scale silver-rich spheroidal GP zones is shown in the enlarged inset in (a).…”

“…The closed assembly morphology adopted by the γ ′ precipitates is therefore determined by the geometry of the stacking fault provided by the dissociated Frank dislocation loop. The separation, r, of the Shockley and stair-rod partials can be estimated (neglecting anisotropy) using the equation [13];…”