Dislocations and faults in some alloys containing copper and aluminum

Abstract

By using the method of variance of the respective X-ray diffraction line profile, the effective particle size (p) and r.m.s.. strain (〈S2〉1/2) of four alloys containing copper and aluminium (Al-0.08, 4 and 10 wt% Cu and Cu-5.87 wt% Al) at different annealing stages (starting from the cold filed stages) have been determined. From the peak shift of these samples, their average stacking fault probability α = α′ − α″ where α′ is the intrinsic stacking fault probability and α″ the corresponding extrinsic stacking fault probability, respectively, were determined. Similarly, from the angular distance between the peak and the centroid of the diffraction profiles, the magnitude ofβ + 4.5α″, whereβ is the twinning fault probability, was measured. From these, the true particle sizeT, the stacking and twinning fault probabilities α′, α″ andβ and the minimum stacking fault widthDmin have been determined. The hardness of alloys at different annealing stages was found to be dependent on the dislocation density and the stored energy in the alloys. The relationT 〈S2〉1/2 = constant was found to be valid for the alloys and from this a mechanism of grain growth with annealing has been suggested. With annealing the dislocation density and stored energy per unit volume were found to decrease until finally, in the fully annealed stages, they disappeared. The same was found to be valid for stacking and twinning fault probabilities as well as the minimum stacking fault width. A mechanism for the creation and annihilation of the intrinsic and extrinsic stacking faults has been suggested.