[Paper Review] Parent grain reconstruction from partially or fully transformed microstructures in MTEX

Frank Niessen, Tuomo Nyyssönen+2 more|arXiv (Cornell University)|Apr 29, 2021

Microstructure and Mechanical Properties of Steels14 citations

TL;DR

This paper presents a universal framework in the open-source MTEX toolbox for reconstructing parent grains from partially or fully transformed microstructures across all crystallographic symmetry combinations. It enables advanced orientation relationship discovery and variant analysis, demonstrated through three real-world applications in steels and titanium alloys with high accuracy and programmable customization.

ABSTRACT

A versatile generic framework for parent grain reconstruction from fully or partially transformed child microstructures was integrated into the open-source crystallographic toolbox MTEX. The framework extends traditional parent grain reconstruction, phase transformation and variant analysis to all parent-child crystal symmetry combinations. The inherent versatility of the universally applicable parent grain reconstruction methods, and the ability to conduct in-depth variant analysis are showcased via example workflows that can be programmatically modified by users to suit their specific applications. This is highlighted by three applications namely, $α$-to-$γ$ reconstruction in a lath martensitic steel, $α$-to-$β$ reconstruction in a Ti alloy, and a two-step reconstruction from $α$-to-$\varepsilon$-to-$γ$ in a twinning and transformation -induced plasticity steel. Advanced orientation relationship discovery and analysis options, including variant analysis, is demonstrated via the add-on function library, ORTools.

Motivation & Objective

• To develop a generic, universally applicable framework for parent grain reconstruction in materials with complex phase transformations.
• To extend traditional reconstruction methods to handle all possible parent-child crystal symmetry combinations.
• To enable in-depth variant analysis and orientation relationship discovery in polycrystalline microstructures.
• To provide a programmable, extensible solution within the MTEX toolbox for researchers to customize workflows.
• To demonstrate the framework's versatility across diverse materials systems, including steels and titanium alloys.

Proposed method

• Integration of a universal parent grain reconstruction algorithm into the open-source MTEX crystallographic toolbox.
• Leveraging group theory and crystallographic symmetry operations to handle arbitrary parent and child phase combinations.
• Implementation of orientation relationship discovery using transformation matrix analysis and symmetry group matching.
• Incorporation of variant analysis tools to identify and classify transformation variants based on crystallographic compatibility.
• Development of the ORTools add-on library to support advanced analysis of orientation relationships and variant selection.
• Design of programmable, user-modifiable workflows for application-specific reconstruction tasks.

Experimental results

Research questions

• RQ1 How can parent grain reconstruction be generalized across all possible crystal symmetry combinations in phase-transformed microstructures?
• RQ2 What is the role of crystallographic symmetry in enabling accurate orientation relationship prediction during phase transformations?
• RQ3 Can variant analysis be systematically applied to identify all possible transformation variants in complex microstructures?
• RQ4 How does the framework enable reliable reconstruction in cases of partial or complete phase transformation?
• RQ5 To what extent can the MTEX-based framework be customized for diverse materials systems and experimental data?

Key findings

• The framework successfully enables parent grain reconstruction for all parent-child crystal symmetry combinations, including complex cases like monoclinic to cubic transformations.
• Variant analysis is systematically performed and visualized, identifying all physically possible transformation variants based on crystallographic compatibility.
• The method achieves high accuracy in reconstructing parent grain structures in lath martensitic steel from α-to-γ transformation, with consistent orientation relationships.
• In Ti alloys, the framework accurately reconstructs parent grains from α-to-β transformations, demonstrating robustness across different symmetry types.
• The two-step reconstruction in a twinning and transformation-induced plasticity (TWIP) steel from α-to-ε-to-γ confirms the framework’s capability in multi-step transformation sequences.
• The ORTools add-on enables detailed analysis of orientation relationships, including symmetry-based variant classification and transformation pathway mapping.