PSI - Issue 43

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2022) 000 – 000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2022) 000 – 000

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ScienceDirect

Procedia Structural Integrity 43 (2023) 234–239

© 2023 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 the responsibility of MSMF10 organizers. © 20 23 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 the responsibility of MSMF10 organizers. Abstract The author describes hi view of how he metal casting process is often carried out turbulently, generat ng doubled-over oxide films (bifilms) in most metal (with interesting exceptions). The double films act as cracks, whose oxide films resist bonding, enabl he crack population to survive plasti working such as forging and rolling. Experimental evidence reveals their actio in i iti t ng tensile and fatig e failur s, and reduci g ductility and creep resistanc . The bifilm cracks are mainly located at rain boundar es, where they encourage th precipitation of inclusions and second phases as a result of the savings of strain energy (far exceeding the normal driving force fro interfacial energies). The precipitates force open he bifilms r ther than otherwise plas ically deforming the matrix to ccomm date the ch nges of size and shape. It is reasonable to suppose that the opening of bifilms at grain boundaries would in ease hydrog n perm ation and embrittleme t, and permit the ingress of corrod nts leading to etch pitting and stress corrosion cracki g. It seems the pre-existing population of microcracks is a phenomenon explaining the initi any of our failure me hanisms in metals. It is strongly recommended to reduce the microcrack population by the application of improved melting and casting technology. © 20 23 The Authors. Published by Elsevier B.V. This is an ope access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under the responsibility of MSMF10 organizers. 10th International Conference on Materials Structure and Micromechanics of Fracture The Pre-Existing Microcrack Population in Metals A Personal Overview John Campbell* Emeritus Professor of Casting Technology, School of Metalllurgy and Materials Faculty of Engineering, University of Birmingham, UK Abstract The author describes his view of how the metal casting process is often carried out turbulently, generating doubled-over oxide films (bifilms) in most metals (with interesting exceptions). The double films act as cracks, whose oxide films resist bonding, enabling the crack population to survive plastic working such as forging and rolling. Experimental evidence reveals their action in initiating tensile and fatigue failures, and reducing ductility and creep resistance. The bifilm cracks are mainly located at grain boundaries, where they encourage the precipitation of inclusions and second phases as a result of the savings of strain energy (far exceeding the normal driving force from interfacial energies). The precipitates force open the bifilms rather than otherwise plastically deforming the matrix to accommodate the changes of size and shape. It is reasonable to suppose that the opening of bifilms at grain boundaries would increase hydrogen permeation and embrittlement, and permit the ingress of corrodents leading to etch pitting and stress corrosion cracking. It seems the pre-existing population of microcracks is a phenomenon explaining the initiation of many of our failure mechanisms in metals. It is strongly recommended to reduce the microcrack population by the application of improved melting and casting technology. 10th International Conference on Materials Structure and Micromechanics of Fracture The Pre-Existing Microcrack Population in Metals A Personal Overview John Campbell* Emeritus Professor of Casting Techno ogy, School of Metalllurgy and Materials Faculty of Eng eering, University of Birmingham, UK

Key Words: Fracture; Cracks; Bifilms; Casting; Fatigue. Key Words: Fracture; Cracks; Bifilms; Casting; Fatigue.

* Corresponding author. Tel.: 44-07802 408 347; fax: +0-000-000-0000 . E-mail address: jc@campbelltech.co.uk * Correspon ing author. Tel.: 44-07802 408 347; fax: +0-000-000-0000 . E-mail address: jc@campbelltech.co.uk

2452-3216 © 2023 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 the responsibility of MSMF10 organizers. 2452-3216 © 2023 The Authors. Published by Elsevier B.V. This is an ope access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under the responsibility of MSMF10 organizers.

2452-3216 © 2023 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 the responsibility of MSMF10 organizers. 10.1016/j.prostr.2022.12.264