Effective structural unit analysis in hexagonal close packed alloys -- reconstruction of parent beta microstructures & crystal orientation post processing analysis

TL;DR

This paper introduces an open-source algorithm for analyzing and reconstructing microstructures in zirconium alloys, focusing on phase transformation relationships and crystal orientations, aiding understanding of deformation properties.

Contribution

It adapts a Markov Chain clustering algorithm for EBSD data to analyze phase variants and orientation relationships in HCP and BCC zirconium alloys, and compares it with existing tools.

Findings

The algorithm effectively reconstructs parent beta microstructures from HCP data.

It reveals shared crystal planes and lattice directions within parent grains.

Comparison with MTEX codes shows consistent and complementary microstructure descriptions.

Abstract

Materials with an allotropic phase transformation can result in the formation of microstructures where grains have orientation relationships (ORs) determined by the transformation history. These microstructures influence the final material properties. In zirconium alloys, there is a solid-state body centred cubic (BCC) to hexagonal close packed (HCP) phase transformation, where the crystal orientations of the HCP phase can be related to the parent BCC structure via the Burgers orientation relationship (BOR). In the present work, we adapt a reconstruction code developed for steels which uses a Markov Chain clustering algorithm to analyse electron backscatter diffraction (EBSD) maps and apply this to the HCP and BCC BOR. This algorithm is released as open-source code (via github, as ParentBOR). The algorithm enables new post processing of the original and reconstructed data set to analyse the variants of the HCP alpha-phase that are present and understand shared crystal planes and shared lattice directions within each parent beta grain, and we anticipate that this assists in understanding the transformation related deformation properties of the final microstructure. Finally, we compare the ParentBOR code with recently released reconstruction codes implemented in MTEX to reveal differences and similarities in how the microstructure is described.