An x-ray diffraction study of lattice imperfections in cold-worked face-centered-cubic alloys. V. Silver-aluminum (α phase)

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X-ray peak-shift, peak-asymmetry, and peak-broadening analyses have been performed on cold-worked α-phase Ag-Al alloys containing 5.8, 9.2, 15.8, and 18.2 at. % Al based on the diffraction profiles recorded with copper radiation and a counter diffractometer equipped with (100) LiF crystal monochromator. Following the procedures adopted earlier in this series of work, a detailed analyses of the recorded profiles revealed quantitative estimates of the microstructural parameters, namely, propensity of stacking faults (intrinsic, extrinsic, and twin faults), rms microstrains, coherent domain sizes, long-range residual stresses, lattice parameter changes, dislocation density, and stacking fault energy. As in earlier alloy systems of this series, the results indicate an increase in the stacking fault density, primarily of intrinsic character with increasing solute concentration, and these are mainly responsible for the observed peak shifts and domain size broadening. Small asymmetry in the profiles has been found to be due to the presence of extrinsic stacking faults, relatively less in magnitude compared to intrinsic ones while the deformation twin faults are almost absent. The dislocation density ρ has been evaluated from the anisotropic values of the coherent domain sizes and rms microstrains. The stacking fault energy γ0 for pure silver has been estimated to be 6–9 mJ/m2, which is lower than the previously reported values. Finally, annealing experiments with Ag-5.8 at. % Al alloy do not show any detectable evidence of solute segregation at stacking faults.