Efficient reconstruction of prior austenite grains in steel from etched light optical micrographs using deep learning and annotations from correlative microscopy

The high-temperature austenite phase is the initial state of practically all technologically relevant hot forming and heat treatment operations in steel processing. The phenomena occurring in austenite, such as recrystallization or grain growth, can have a decisive influence on the subsequent proper...

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Main Authors: Björn-Ivo Bachmann, Martin Müller, Dominik Britz, Ali Riza Durmaz, Marc Ackermann, Oleg Shchyglo, Thorsten Staudt, Frank Mücklich
Format: Article
Language:English
Published: Frontiers Media S.A. 2022-10-01
Series:Frontiers in Materials
Subjects:
Online Access:https://www.frontiersin.org/articles/10.3389/fmats.2022.1033505/full
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author Björn-Ivo Bachmann
Björn-Ivo Bachmann
Martin Müller
Martin Müller
Dominik Britz
Dominik Britz
Ali Riza Durmaz
Marc Ackermann
Oleg Shchyglo
Thorsten Staudt
Frank Mücklich
Frank Mücklich
author_facet Björn-Ivo Bachmann
Björn-Ivo Bachmann
Martin Müller
Martin Müller
Dominik Britz
Dominik Britz
Ali Riza Durmaz
Marc Ackermann
Oleg Shchyglo
Thorsten Staudt
Frank Mücklich
Frank Mücklich
author_sort Björn-Ivo Bachmann
collection DOAJ
description The high-temperature austenite phase is the initial state of practically all technologically relevant hot forming and heat treatment operations in steel processing. The phenomena occurring in austenite, such as recrystallization or grain growth, can have a decisive influence on the subsequent properties of the material. After the hot forming or heat treatment process, however, the austenite transforms into other microstructural constituents and information on the prior austenite morphology are no longer directly accessible. There are established methods available for reconstructing former austenite grain boundaries via metallographic etching or electron backscatter diffraction (EBSD) which both exhibit shortcomings. While etching is often difficult to reproduce and strongly depend on the investigated steel’s alloying concept, EBSD acquisition and reconstruction is rather time-consuming. But in fact, though, light optical micrographs of steels contrasted with conventional Nital etchant also contain information about the former austenite grains. However, relevant features are not directly apparent or accessible with conventional segmentation approaches. This work presents a deep learning (DL) segmentation of prior austenite grains (PAG) from Nital etched light optical micrographs. The basis for successful segmentation is a correlative characterization from EBSD, light and scanning electron microscopy to specify the ground truth required for supervised learning. The DL model shows good and robust segmentation results. While the intersection over union of 70% does not fully reflect the model performance due to the inherent uncertainty in PAG estimation, a mean error of 6.1% in mean grain size derived from the segmentation clearly shows the high quality of the result.
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spelling doaj.art-0d528dbce9a84a30a9c196d7c90d36b52022-12-22T02:24:20ZengFrontiers Media S.A.Frontiers in Materials2296-80162022-10-01910.3389/fmats.2022.10335051033505Efficient reconstruction of prior austenite grains in steel from etched light optical micrographs using deep learning and annotations from correlative microscopyBjörn-Ivo Bachmann0Björn-Ivo Bachmann1Martin Müller2Martin Müller3Dominik Britz4Dominik Britz5Ali Riza Durmaz6Marc Ackermann7Oleg Shchyglo8Thorsten Staudt9Frank Mücklich10Frank Mücklich11Department of Materials Science, Saarland University, Saarbruecken, GermanyMaterial Engineering Center Saarland, Saarbruecken, GermanyDepartment of Materials Science, Saarland University, Saarbruecken, GermanyMaterial Engineering Center Saarland, Saarbruecken, GermanyDepartment of Materials Science, Saarland University, Saarbruecken, GermanyMaterial Engineering Center Saarland, Saarbruecken, GermanyFraunhofer Institute for Mechanics of Materials IWM, Freiburg, GermanySteel Institute, RWTH Aachen University, Aachen, GermanyInterdisciplinary Centre for Advanced Materials Simulation (ICAMS), Ruhr-Universität Bochum, Bochum, GermanyAktien-Gesellschaft der Dillinger Hüttenwerke, Dillingen, GermanyDepartment of Materials Science, Saarland University, Saarbruecken, GermanyMaterial Engineering Center Saarland, Saarbruecken, GermanyThe high-temperature austenite phase is the initial state of practically all technologically relevant hot forming and heat treatment operations in steel processing. The phenomena occurring in austenite, such as recrystallization or grain growth, can have a decisive influence on the subsequent properties of the material. After the hot forming or heat treatment process, however, the austenite transforms into other microstructural constituents and information on the prior austenite morphology are no longer directly accessible. There are established methods available for reconstructing former austenite grain boundaries via metallographic etching or electron backscatter diffraction (EBSD) which both exhibit shortcomings. While etching is often difficult to reproduce and strongly depend on the investigated steel’s alloying concept, EBSD acquisition and reconstruction is rather time-consuming. But in fact, though, light optical micrographs of steels contrasted with conventional Nital etchant also contain information about the former austenite grains. However, relevant features are not directly apparent or accessible with conventional segmentation approaches. This work presents a deep learning (DL) segmentation of prior austenite grains (PAG) from Nital etched light optical micrographs. The basis for successful segmentation is a correlative characterization from EBSD, light and scanning electron microscopy to specify the ground truth required for supervised learning. The DL model shows good and robust segmentation results. While the intersection over union of 70% does not fully reflect the model performance due to the inherent uncertainty in PAG estimation, a mean error of 6.1% in mean grain size derived from the segmentation clearly shows the high quality of the result.https://www.frontiersin.org/articles/10.3389/fmats.2022.1033505/fullsteelprior austenite grainssegmentationmachine learning/deep learningquantification
spellingShingle Björn-Ivo Bachmann
Björn-Ivo Bachmann
Martin Müller
Martin Müller
Dominik Britz
Dominik Britz
Ali Riza Durmaz
Marc Ackermann
Oleg Shchyglo
Thorsten Staudt
Frank Mücklich
Frank Mücklich
Efficient reconstruction of prior austenite grains in steel from etched light optical micrographs using deep learning and annotations from correlative microscopy
Frontiers in Materials
steel
prior austenite grains
segmentation
machine learning/deep learning
quantification
title Efficient reconstruction of prior austenite grains in steel from etched light optical micrographs using deep learning and annotations from correlative microscopy
title_full Efficient reconstruction of prior austenite grains in steel from etched light optical micrographs using deep learning and annotations from correlative microscopy
title_fullStr Efficient reconstruction of prior austenite grains in steel from etched light optical micrographs using deep learning and annotations from correlative microscopy
title_full_unstemmed Efficient reconstruction of prior austenite grains in steel from etched light optical micrographs using deep learning and annotations from correlative microscopy
title_short Efficient reconstruction of prior austenite grains in steel from etched light optical micrographs using deep learning and annotations from correlative microscopy
title_sort efficient reconstruction of prior austenite grains in steel from etched light optical micrographs using deep learning and annotations from correlative microscopy
topic steel
prior austenite grains
segmentation
machine learning/deep learning
quantification
url https://www.frontiersin.org/articles/10.3389/fmats.2022.1033505/full
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