Higher order laue zone patterns in convergent beam electron diffraction and determinations of local lattice parameters in a- and a₂-phases of a cu-20at%ai alloy

In order to clarify the applicability of higher order Laue zone (HOLZ) patterns in convergent beam electron diffraction to the determinations of local lattice distortions in two-phase alloys, we discussed experimental conditions affecting the accuracy, and observed HOLZ patterns of a Cu-20at%AI alloy, in which small particles of a₂-phase with one dimensional long period superstructure are precipitated in the matrix of fee α-phase. It was shown that the accuracy is affected by specimen thickness as well as beam direction, and that lattice parameters along the [100] and [010] axes can be determined from a [114] HOLZ pattern with an error less than one part in a thousand. The [114] HOLZ patterns were obtained both from small regions in α-matrix and a₂-particles. Slight changes in lattice parameters were detected as a function of position with a high spatial resolution.