PSI - Issue 43

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Procedia Structural Integrity 43 (2023) 197–202

10th International Conference on Materials Structure and Micromechanics of Fracture Mechanisms of intergranular fatigue crack initiation in 10th International Conference on Materials Structure and Micromechanics of Fracture Mechanisms of intergranular fatigue crack initiation in

polycrystalline materials Jaroslav Polák *, Alice Chlupová Institute f Physics of Materials, Czech Academy f Sciences, Brno, 616 00, Czechia polycrystalline materials Jaroslav Polák *, Alice Chlupová Institute f Physics of Materials, Czech Academy f Sciences, Brno, 616 00, Czechia

© 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. transgran lar fatigue crack initiation int rgr nular in tiation is sti l the subject of controversy. A recent study of the cr ck tiation in superaustenitic Sanicro 25 steel [1] revealed the important role of pers stent lip markings (PSMs) n the grains adjoining the g ain boundary. A novel mechanism of i t rgran lar fatigue c ack initiatio has bee proposed. Provided the cyclic slip cannot pr ceed from one grain to the neighbour on , xtrusions and trusion ari e not only on the surf ce but also on the gr in bo ndary. Growing intrusions repres nt void-lik defects and growing intrusions push neighbour grain part. A ystematic study of intergranular cracking has b en performed polycryst lline copper cycled with high and low st ai mplitudes. SEM observations of the early stages of fatig e crack ini i ti n the grain boundar es, EBSD study of grains or entation, FIB cutt ng of th g ain bound ri s and simultane us d cumentation of the effect of extrusions nd intrusions on the grain boundary cohesion are reported simultaneously with the conditions favourable for the initiation of the fatigue cracks. © 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. Abstract Fatigue failure in polycrystalline materials occurs by initiation and propagation of fatigue cracks. Fatigue cracks can initiate transgranularly or intergranularly. While considerable progress has been achieved in the explanation of the mechanism of transgranular fatigue crack initiation intergranular initiation is still the subject of controversy. A recent study of the crack initiation in superaustenitic Sanicro 25 steel [1] revealed the important role of persistent slip markings (PSMs) in the grains adjoining the grain boundary. A novel mechanism of intergranular fatigue crack initiation has been proposed. Provided the cyclic slip cannot proceed from one grain to the neighbour one, extrusions and intrusions arise not only on the surface but also on the grain boundary. Growing intrusions represent void-like defects and growing intrusions push neighbour grain apart. A systematic study of intergranular cracking has been performed on polycrystalline copper cycled with high and low strain amplitudes. SEM observations of the early stages of fatigue crack initiation on the grain boundaries, EBSD study of grains orientation, FIB cutting of the grain boundaries and simultaneous documentation of the effect of extrusions and intrusions on the grain boundary cohesion are reported simultaneously with the conditions favourable for the initiation of the fatigue cracks. Abstract F tigue failure in polycrystal ine materials ccurs by initiation and propag tion of fatigu cracks. Fatigue cracks an nitiate ly or intergra ularly. While considerable progress as be n achieved in the expla ation of me ha sm f

Keywords: fatigue crack; intergranular initiation; extrusions; intrusions; grain boundary damage Keywords: fatigue crack; intergranular initiation; extrusions; intrusions; grain boundary damage

* Corresponding author. Tel.: +420 532 290 366 E-mail address: polak@ipm.cz * Correspon ing author. Tel.: +420 532 290 366 E-mail address: polak@ipm.cz

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 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 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.2022.12.258