PSI - Issue 68

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ScienceDirect

Procedia Structural Integrity 68 (2025) 1045–1050 Procedia Structural Integrity 00 (2024) 000–000 Procedia Structural Integrity 00 (2024) 000–000

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European Conference on Fracture 2024 Microstructure Based Analysis of Plasticity and Failure of Dual Phase Steels Eren C¸ elikses a, ∗ , ˙Ibrahim Yelek a , Merthan O¨ zdemir b , Tuncay Yalc¸inkaya b a Borcelik Steel Industry Trade Inc. R & D Center, Bursa 16601, Tu¨rkiye b Department of Aerospace Engineering, Middle East Technical University, Ankara 06800, Tu¨rkiye Abstract The formability and performance of dual-phase (DP) steel are determined by its microstructural characteristics. A banded marten sitic microstructure can lead to premature failure during forming operations. In this study, two DP800 steel samples, one with a banded martensite structure and the other with an evenly dispersed martensite structure, are characterized through Nakazima and hole expansion experiments. Although both samples exhibit similar levels of ductility in tensile tests, their performance in forming experiments di ff ers significantly. To further investigate the e ff ect of microstructural banding, finite element models are generated from micrographs of the two samples using an in-house script. The plastic responses of the ferrite and martensite phases are cali brated to experimental data. These representative models are analysed under di ff erent loading scenarios to examine the impact of banding on the plasticity and failure of DP steels. The study concludes that martensite banding can induce anisotropic material behavior locally, leading to premature strain localization and, ultimately, early failure of the specimen. © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of ECF24 organizers. Keywords: Dual phase steels; Banded microstructure; Forming limit diagram; Micromechanical analysis European Conference on Fracture 2024 Microstructure Based Analysis of Plasticity and Failure of Dual Phase Steels Eren C¸ elikses a, ∗ , ˙Ibrahim Yelek a , Merthan O¨ zdemir b , Tuncay Yalc¸inkaya b a Borcelik Steel Industry Trade Inc. R & D Center, Bursa 16601, Tu¨rkiye b Department of Aerospace Engineering, Middle East Technical University, Ankara 06800, Tu¨rkiye Abstract The formability and performance of dual-phase (DP) steel are determined by its microstructural characteristics. A banded marten sitic microstructure can lead to premature failure during forming operations. In this study, two DP800 steel samples, one with a banded martensite structure and the other with an evenly dispersed martensite structure, are characterized through Nakazima and hole expansion experiments. Although both samples exhibit similar levels of ductility in tensile tests, their performance in forming experiments di ff ers significantly. To further investigate the e ff ect of microstructural banding, finite element models are generated from micrographs of the two samples using an in-house script. The plastic responses of the ferrite and martensite phases are cali brated to experimental data. These representative models are analysed under di ff erent loading scenarios to examine the impact of banding on the plasticity and failure of DP steels. The study concludes that martensite banding can induce anisotropic material behavior locally, leading to premature strain localization and, ultimately, early failure of the specimen. © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of ECF24 organizers. Keywords: Dual phase steels; Banded microstructure; Forming limit diagram; Micromechanical analysis © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers

1. Introduction 1. Introduction

Dual-phase (DP) steels are among the most widely used grades within Advanced High Strength Steels (AHSS) due to their exceptional mechanical properties, corrosion resistance, and relatively low production costs. As highlighted in Taub et al. (2019), interest in these grades has grown significantly in recent years, driven by the automotive industry’s increasing focus on weight reduction. DP steels feature a unique microstructure consisting of soft-phase ferrite and hard-phase martensite, which together provide an optimal balance of ductility and strength. These steels are typically produced through intercritical annealing of cold-rolled materials, followed by rapid quenching. During intercritical annealing, the rolled microstructure is austenitized, resulting in a combination of ferrite and austenite as discussed in Tasan et al. (2015). Quenching then transforms the austenite into martensite, forming the distinctive dual-phase Dual-phase (DP) steels are among the most widely used grades within Advanced High Strength Steels (AHSS) due to their exceptional mechanical properties, corrosion resistance, and relatively low production costs. As highlighted in Taub et al. (2019), interest in these grades has grown significantly in recent years, driven by the automotive industry’s increasing focus on weight reduction. DP steels feature a unique microstructure consisting of soft-phase ferrite and hard-phase martensite, which together provide an optimal balance of ductility and strength. These steels are typically produced through intercritical annealing of cold-rolled materials, followed by rapid quenching. During intercritical annealing, the rolled microstructure is austenitized, resulting in a combination of ferrite and austenite as discussed in Tasan et al. (2015). Quenching then transforms the austenite into martensite, forming the distinctive dual-phase

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers 10.1016/j.prostr.2025.06.168 ∗ Corresponding author. Tel.: + 90-224-280-4000 ; fax: + 90-224-519-0130. E-mail address: ecelikses@borcelik.com 2210-7843 © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of ECF24 organizers. ∗ Corresponding author. Tel.: + 90-224-280-4000 ; fax: + 90-224-519-0130. E-mail address: ecelikses@borcelik.com 2210-7843 © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of ECF24 organizers.