Orientation reconstruction of transformation $\alpha$ titanium alloys via polarized light microscopy: methodology and assessment

TL;DR

This paper presents a novel method using polarized light microscopy to reconstruct the complete crystallographic orientations of alpha titanium alloys by leveraging the Burgers orientation relationship, improving microstructural analysis and deformation predictions.

Contribution

The study introduces a new orientation reconstruction technique for titanium alloys using PLM, capable of narrowing down orientations to four possibilities based on the Burgers relationship.

Findings

The method effectively reconstructs orientations in idealized samples.

Significant improvement in deformation predictions when using reconstructed orientations.

Demonstrated applicability in informing crystal plasticity simulations.

Abstract

Emerging microstructural characterization methods have received increased attention owing to their promise of relatively inexpensive and rapid measurement of polycrystalline surface morphology and crystallographic orientations. Among these nascent methods, polarized light microscopy (PLM) is attractive for characterizing alloys comprised of hexagonal crystals, but is hindered by its inability to measure complete crystal orientations. In this study, we explore the potential to reconstruct quasi-deterministic orientations for titanium microstructures characterized via PLM by considering the Burgers orientation relationship between the room temperature $\alpha$ (HCP) phase fibers measured via PLM, and the $\beta$ (BCC) phase orientations of the parent grains present above the transus temperature. We describe this method -- which is capable of narrowing down the orientations to one of four possibilities -- and demonstrate its abilities on idealized computational samples in which the parent $\beta$ microstructure is fully, unambiguously known. We further utilize this method to inform the instantiation of samples for crystal plasticity simulations, and demonstrate the significant improvement in deformation field predictions when utilizing this reconstruction method compared to using results from traditional PLM.