Parent grain reconstruction from partially or fully transformed microstructures in MTEX.

Frank Niessen,Tuomo Nyyssönen,Ralf Hielscher,Azdiar A Gazder

doi:10.1107/s1600576721011560

Abstract

A versatile generic framework for parent grain reconstruction from fully or partially transformed child microstructures has been 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 ɛ to γ in a twinning and transformation-induced plasticity steel. Advanced orientation relationship discovery and analysis options, including variant analysis, are demonstrated via the add-on function library ORTools.

Highlights

Depending on the chemistry and thermomechanical processing history of a material system, its free energy difference may lead to the phase transformation of a pre-existing parent phase with a given crystal symmetry to a new child phase with a similar or different crystal symmetry (Porter & Easterling, 1992)
An orientation relationship (OR) refers to the coherent geometric parallelism between specific planes and directions of parent–child crystal symmetries on either side of their common boundary segment (Bhadeshia, 1991)
In all parent–child crystal symmetry combinations, one or more favoured ORs exist that provide the best fit at their boundary segment interfaces and enable crystallographic phase transformation between them

Summary

Introduction

Depending on the chemistry and thermomechanical processing history of a material system, its free energy difference may lead to the phase transformation of a pre-existing parent phase with a given crystal symmetry to a new child phase with a similar or different crystal symmetry (Porter & Easterling, 1992). In many instances, this phase transformation occurs via the operation of an orientation relationship (OR). Depending on the circumstances of the phase transformation, variant selection may occur when only a few of the theoretically predicted child orientation variants dominate the partially or fully transformed microstructure

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Discussion

Conclusion