PSI - Issue 68

Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2025) 000–000 Available online at www.sciencedirect.com ScienceDirect

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Procedia Structural Integrity 68 (2025) 513–519

European Conference on Fracture 2024 Quantitative fractography in the DBT regime of 9Cr-1Mo ferritic/martensitic steel Swastik Soni a , Abhishek Tiwari a *, R.N. Singh b a Department of Metallurgical and Materials Engineering, IIT Ropar, Punjab, 140001, India b Mechanical Metallurgy Division, BARC, Mumbai, Maharashtra, 400085, India Abstract In this work quantitative fractography using average dimple diameter and fractal dimensions is investigated in the ductile to brittle transition (DBT) regime of 9Cr-1Mo steel at varying strain rates. The tensile experiments were conducted at different strain rates (in range of 3x10 -4 per seconds to 18x10 -3 per seconds) and varying temperature (ranging from -20°C to -70°C). The Fractographic examinations were used to characterize the DBT regime as the features showed decreasing dimple size with increasing strain rate. The influence of strain rate was also characterized using fractal dimension of a material's fracture surface determined by box count method. The dimple diameter and fractal dimension were in agreement with the strain rate influence. © 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 Keywords: Quantitative Fractography; DBT regime; Fractal dimension; Strain rate; Fracture. 1. Introduction The ductile to brittle transition (DBT) is a critical phenomenon that affects the mechanical performance of ferritic/martensitic steels, such as Mod 9Cr-1Mo steel, commonly used in high-temperature applications like power plants and nuclear reactors. Understanding how factors like strain rate and temperature influence this transition is essential for ensuring the reliability of materials under stress. © 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

* Corresponding author. Tel.: +91 8452016193 E-mail address: abhishek.tiwari@iitrpr.ac.in

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

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.2025.06.090