Fatigue Crack Initiation Change of Cast AZ91 Magnesium Alloy from Low to Very High Cycle Fatigue Region

Fintová, Stanislava; Trško, Libor; Chlup, Zdeněk; Pastorek, Filip; Kajánek, Daniel; Kunz, Ludvík

doi:10.3390/ma14216245

Open AccessArticle

Fatigue Crack Initiation Change of Cast AZ91 Magnesium Alloy from Low to Very High Cycle Fatigue Region

by

Stanislava Fintová

^1,*

,

Libor Trško

²

,

Zdeněk Chlup

¹

,

Filip Pastorek

²,

Daniel Kajánek

² and

Ludvík Kunz

¹

Institute of Physics of Materials, Czech Academy of Sciences, Žižkova 22, 616 00 Brno, Czech Republic

²

Research Centre, University of Žilina, Univerzitná 8215/1, 010 26 Žilina, Slovakia

^*

Author to whom correspondence should be addressed.

Materials 2021, 14(21), 6245; https://doi.org/10.3390/ma14216245

Submission received: 13 September 2021 / Revised: 12 October 2021 / Accepted: 15 October 2021 / Published: 20 October 2021

(This article belongs to the Special Issue Fatigue Crack Growth in Metallic Materials)

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Abstract

Fatigue tests were performed on the AZ91 cast alloy to identify the mechanisms of the fatigue crack initiation. In different fatigue regions, different mechanisms were observed. In the low and high cycle fatigue regions, slip markings formation accompanied with Mg₁₇Al₁₂ particles cracking were observed. Slip markings act as the fatigue crack initiation sites. The size and number of slip markings decreased with decreased stress amplitude applied. When slip markings formation was suppressed due to low stress amplitude, particle cracking became more important and the cracks continued to grow through the particle/solid solution interface. The change of the fatigue crack initiation mechanisms led the S-N curve to shift to the higher number of cycles to the fracture, demonstrated by its stepwise character. A lower fatigue limit of 60 MPa was determined at 20 kHz for 2 × 10⁹ cycles compared to the 80 MPa determined at 60 Hz for 1 × 10⁷ cycles.

Keywords: Mg; fatigue mechanism; microstructure; focused ion beam (FIB); scanning electron microscopy (SEM)

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Fintová, S.; Trško, L.; Chlup, Z.; Pastorek, F.; Kajánek, D.; Kunz, L. Fatigue Crack Initiation Change of Cast AZ91 Magnesium Alloy from Low to Very High Cycle Fatigue Region. Materials 2021, 14, 6245. https://doi.org/10.3390/ma14216245

AMA Style

Fintová S, Trško L, Chlup Z, Pastorek F, Kajánek D, Kunz L. Fatigue Crack Initiation Change of Cast AZ91 Magnesium Alloy from Low to Very High Cycle Fatigue Region. Materials. 2021; 14(21):6245. https://doi.org/10.3390/ma14216245

Chicago/Turabian Style

Fintová, Stanislava, Libor Trško, Zdeněk Chlup, Filip Pastorek, Daniel Kajánek, and Ludvík Kunz. 2021. "Fatigue Crack Initiation Change of Cast AZ91 Magnesium Alloy from Low to Very High Cycle Fatigue Region" Materials 14, no. 21: 6245. https://doi.org/10.3390/ma14216245

APA Style

Fintová, S., Trško, L., Chlup, Z., Pastorek, F., Kajánek, D., & Kunz, L. (2021). Fatigue Crack Initiation Change of Cast AZ91 Magnesium Alloy from Low to Very High Cycle Fatigue Region. Materials, 14(21), 6245. https://doi.org/10.3390/ma14216245

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Fatigue Crack Initiation Change of Cast AZ91 Magnesium Alloy from Low to Very High Cycle Fatigue Region

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