Mapping of Local Lattice Parameter Ratios by Projective Kikuchi Pattern Matching

TL;DR

This paper introduces a novel method for analyzing local lattice distortions in crystal structures using Kikuchi pattern matching in EBSD, enabling detailed mapping of lattice parameter ratios.

Contribution

It presents a new projective transformation-based approach for quantitatively estimating local lattice distortions from EBSD Kikuchi patterns.

Findings

Successfully mapped local tetragonality in steel martensite.

Achieved continuous estimation of lattice distortions.

Provided a crystallographically consistent fitting method.

Abstract

We describe a lattice-based crystallographic approximation for the analysis of distorted crystal structures via Electron Backscatter Diffraction (EBSD) in the scanning electron microscope. EBSD patterns are closely linked to local lattice parameter ratios via Kikuchi bands that indicate geometrical lattice plane projections. Based on the transformation properties of points and lines in the real projective plane, we can obtain continuous estimations of the local lattice distortion based on projectively transformed Kikuchi diffraction simulations for a reference structure. By quantitative image matching to a projective transformation model of the lattice distortion in the full solid angle of possible scattering directions, we enforce a crystallographically consistent approximation in the fitting procedure of distorted simulations to the experimentally observed diffraction patterns. As an application example, we map the locally varying tetragonality in martensite grains of steel.