Effective structural unit analysis in hexagonal close-packed alloys - reconstruction of parent β microstructures and...

Materials that undergo allotropic phase transformations often develop microstructures with orientation relationships based on transformation history. These relationships can impact mechanical properties. In zirconium alloys, a solid-state transformation from body-centred cubic (b.c.c.) to hexagonal close-packed (h.c.p.) occurs. This transformation follows the Burgers orientation relationship (BOR), linking the two phases. Prior research has shown that the crystallographic orientation of the h.c.p. α phase relates to the parent b.c.c. β phase. However, no prior work had resolved how to systematically reconstruct and analyze these relationships in zirconium alloys. This gap motivated the adaptation of existing reconstruction tools for use in this system. Existing methods, such as electron backscatter diffraction (EBSD), provide data but lack tools to fully interpret the transformation history. The lack of post-processing algorithms for h.c.p./b.c.c. systems limited the understanding of microstructure evolution. This paper introduces a new approach to address these limitations.

This study aimed to adapt and apply a reconstruction algorithm originally developed for steels to zirconium alloys undergoing b.c.c. to h.c.p. transformation. The goal was to enable detailed analysis of crystal orientation relationships using EBSD data. The researchers sought to improve understanding of how the α phase forms from the β phase during transformation. They also aimed to release this algorithm as open-source software for broader use. The study focused on the Burgers orientation relationship (BOR) between the two phases. The researchers wanted to determine how variants of the h.c.p. α phase relate to the parent b.c.c. β grains. They also intended to compare their approach with existing tools like MTEX. The study's purpose was to provide a new computational method for analyzing transformation-related microstructures in zirconium alloys.

The researchers adapted a reconstruction algorithm originally developed for steels to analyze EBSD data in zirconium alloys. This algorithm uses a Markov chain clustering approach to identify orientation relationships. The adapted code was released as open-source software called ParentBOR. The algorithm processes EBSD maps to reconstruct the parent β microstructure from the h.c.p. α phase. It identifies crystallographic variants of the α phase and their relationships to the β grains. The code also enables post-processing to determine shared crystal planes and lattice directions. The researchers compared their method with recently developed reconstruction tools in MTEX. The comparison focused on differences in how each method describes the microstructure and orientation relationships.

The adapted algorithm successfully reconstructed the parent β microstructure from the h.c.p. α phase in zirconium alloys. The code identified variants of the α phase and their crystallographic orientation relationships with the β grains. The algorithm enabled post-processing to determine shared crystal planes and lattice directions within each β grain. The results showed that the code could accurately track the transformation history of individual grains. The researchers demonstrated that the algorithm can be used to analyze deformation properties related to the transformation. The code was compared with MTEX tools, revealing similarities in microstructure description but differences in implementation. The comparison highlighted how each method captures orientation relationships differently. The open-source nature of ParentBOR allows for further development and application in similar materials.

The study concludes that the adapted reconstruction algorithm can effectively analyze orientation relationships in zirconium alloys undergoing b.c.c. to h.c.p. transformation. The researchers propose that this method can improve understanding of transformation-related deformation properties. The open-source release of the code enables broader application in materials science. The comparison with MTEX tools revealed differences in how each method describes the microstructure. The study suggests that the algorithm can be used to analyze shared crystal planes and lattice directions. The results support the use of the algorithm for post-processing EBSD data in zirconium alloys. The researchers propose that the method can assist in understanding the microstructural evolution during phase transformations. The study highlights the importance of computational tools in analyzing complex microstructures.