Influence of Humid Environment on Fatigue Behaviour of Cast AM60B Magnesium
Biallas, Gerhard and Maier, Hans Jürgen and Gall, Ken (2006) Influence of Humid Environment on Fatigue Behaviour of Cast AM60B Magnesium. In: Proc. 9th Int. Fatigue Congress. Elsevier (UK). Fatigue 2006, 2006-05-14 - 2006-05-19, Atlanta, GA (USA).
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Low-cycle fatigue (LCF) tests were performed on cast AM60B Mg at room temperature in a high vacuum, at ambient conditions, and in 20 Torr pure water vapor (100 % relative humidity at room temperature). Surprisingly, fatigue life increased in the case of cycling in a humid atmosphere as compared to loading in vacuum. This behavior is attributed to the surface film formed on magnesium by water vapor, which suppresses slip band formation, but favors crack initiation in interdendritic regions. Consequently, only few fatigue cracks are formed early in fatigue life in water vapor, and link-up of these cracks is retarded. The number of cycles to crack initiation is much larger in vacuum environment. However, a high number of slip bands is formed early in fatigue life throughout the specimen surface. Many small cracks nucleate at these slip bands and then rapidly link-up to form the fatal crack that causes premature failure. To rationalize the effect of a humid environment, a plasticity-enhanced hydration mechanism is proposed. Hydration of the surface film on magnesium is intensified for aluminum contents below 4 wt%, which is the case for the primary α-Mg within the dendrite cells of AM60B. Plasticity-induced enhancement of the hydration prevents crack initiation at slip bands within dendrite cells in the LCF range.
|Document Type:||Conference or Workshop Item (Paper)|
|Title:||Influence of Humid Environment on Fatigue Behaviour of Cast AM60B Magnesium|
|Journal or Publication Title:||Proc. 9th Int. Fatigue Congress|
|In ISI Web of Science:||No|
|Keywords:||cast AM60B magnesium, in-situ fatigue, slip bands, small cracks, environmental degradation, surface film, hydrogen embrittlement, damage mechanisms|
|Event Title:||Fatigue 2006|
|Event Location:||Atlanta, GA (USA)|
|Event Type:||international Conference|
|Event Dates:||2006-05-14 - 2006-05-19|
|HGF - Research field:||Aeronautics, Space and Transport|
|HGF - Program:||Aeronautics|
|HGF - Program Themes:||L AR - Aircraft Research|
|DLR - Research area:||Aeronautics|
|DLR - Program:||L AR - Aircraft Research|
|DLR - Research theme (Project):||L - Structures & Materials|
|Institutes and Institutions:||Institute of Materials Research > Mechanical Testing of Materials|
|Deposited By:||Dr.-Ing. Gerhard Biallas|
|Deposited On:||23 Nov 2006|
|Last Modified:||27 Apr 2009 04:55|
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