Lattice Spacings from Lattice Fringes

P. G. Self, H. K. D. H. Bhadeshia and W. M. Stobbs

Abstract

The different techniques available for the accurate measurement of lattice fringe spacings are discussed and their relative merits under different cricumstances assessed. The relationship between the lattice fringe spacing and the lattice parameter is further examined for both uniform and chemically inhomogeneous material. The techniques described were also applied to an investigation of carbon segregation in residual austenite after the upper bainitic transformation in two steels.

The provided text examines various methodologies for calculating lattice fringe spacings using high-resolution transmission electron microscopy. The authors evaluate the effectiveness of moire patterns, microdensitometry, and optical transformation for interpreting these microscopic images. They emphasise that instrumental parameters, such as objective lens focus, can significantly alter observed spacings, leading to results that do not always match the true physical structure. To mitigate these discrepancies, the study suggests analyzing through focal series to obtain more reliable measurements of material properties. Finally, the research applies these techniques to investigate carbon segregation in steel alloys, demonstrating that captured data can reveal inhomogeneous distribution within a crystal lattice.

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