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Environmentally influenced microstructurally small fatigue crack growth in cast magnesium

Publication ,  Journal Article
Gall, K; Biallas, G; Maier, HJ; Horstemeyer, MF; McDowell, DL
Published in: Materials Science and Engineering: A
April 15, 2005

We examine the growth of microstructurally small fatigue cracks in cast AM60B magnesium (Mg) cycled in a water vapor environment. The behavior and growth rates of the small cracks were measured in situ during cycling using a fatigue loading stage contained within an environmental scanning electron microscope (ESEM). We provide quantitative data describing the interaction of representative small fatigue cracks with microstructural features, along with the average growth rate data for approximately 20 different cracks. Small surface and corner cracks, with sizes ranging from 20 to 200 μm, are observed to interact strongly with the surface microstructure during growth. The small cracks preferentially propagate through the dendrite cells, and the particle laden interdendritic regions typically act as barriers to fatigue crack propagation. As the small cracks approach the interdendritic boundaries, measured growth rates decrease and the cracks sometimes becomes temporarily pinned at the boundary. Cracks smaller than 100 μm experience more significant disruptions in crack growth rates at interdendritic boundaries compared to the larger cracks that interact with the boundaries, but with less change in crack growth rates. Under nominally identical loading conditions, isolated microstructurally small cracks grow, on average, two orders of magnitude faster in a sample containing a higher fraction of porosity. The significantly higher crack growth rates in the more porous sample were attributed to local amplification of the nominal stress field in the vicinity of the microstructurally small cracks rather than explicit interactions between growing cracks and pores. Analogous to the wrought materials, the growth rate of microstructurally small cracks is observed to be significantly higher compared to long fatigue cracks at equivalent maximum cyclic stress intensity values. © 2005 Elsevier B.V. All rights reserved.

Duke Scholars

Published In

Materials Science and Engineering: A

DOI

ISSN

0921-5093

Publication Date

April 15, 2005

Volume

396

Issue

1-2

Start / End Page

143 / 154

Related Subject Headings

  • Materials
  • 4017 Mechanical engineering
  • 4016 Materials engineering
  • 0913 Mechanical Engineering
  • 0912 Materials Engineering
  • 0910 Manufacturing Engineering
 

Citation

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ICMJE
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Gall, K., Biallas, G., Maier, H. J., Horstemeyer, M. F., & McDowell, D. L. (2005). Environmentally influenced microstructurally small fatigue crack growth in cast magnesium. Materials Science and Engineering: A, 396(1–2), 143–154. https://doi.org/10.1016/j.msea.2005.01.014
Gall, K., G. Biallas, H. J. Maier, M. F. Horstemeyer, and D. L. McDowell. “Environmentally influenced microstructurally small fatigue crack growth in cast magnesium.” Materials Science and Engineering: A 396, no. 1–2 (April 15, 2005): 143–54. https://doi.org/10.1016/j.msea.2005.01.014.
Gall K, Biallas G, Maier HJ, Horstemeyer MF, McDowell DL. Environmentally influenced microstructurally small fatigue crack growth in cast magnesium. Materials Science and Engineering: A. 2005 Apr 15;396(1–2):143–54.
Gall, K., et al. “Environmentally influenced microstructurally small fatigue crack growth in cast magnesium.” Materials Science and Engineering: A, vol. 396, no. 1–2, Apr. 2005, pp. 143–54. Scopus, doi:10.1016/j.msea.2005.01.014.
Gall K, Biallas G, Maier HJ, Horstemeyer MF, McDowell DL. Environmentally influenced microstructurally small fatigue crack growth in cast magnesium. Materials Science and Engineering: A. 2005 Apr 15;396(1–2):143–154.
Journal cover image

Published In

Materials Science and Engineering: A

DOI

ISSN

0921-5093

Publication Date

April 15, 2005

Volume

396

Issue

1-2

Start / End Page

143 / 154

Related Subject Headings

  • Materials
  • 4017 Mechanical engineering
  • 4016 Materials engineering
  • 0913 Mechanical Engineering
  • 0912 Materials Engineering
  • 0910 Manufacturing Engineering