elib
DLR-Header
DLR-Logo -> http://www.dlr.de
DLR Portal Home | Imprint | Contact | Deutsch
Fontsize: [-] Text [+]

In-situ observations of high cycle fatigue mechanisms in cast AM60B magnesium in vacuum and water vapor environments

Gall, Ken and Biallas, Gerhard and Maier, Hans Jürgen and Gullett, Phil and Horstemeyer, Mark F. and McDowell, David L. and Fan, Jinghong (2004) In-situ observations of high cycle fatigue mechanisms in cast AM60B magnesium in vacuum and water vapor environments. International Journal of Fatigue, 26 (1), pp. 59-70.

Full text not available from this repository.

Abstract

We present in situ scanning electron microscopy (SEM) observations regarding the formation and propagation of small fatigue cracks in cast AM60B magnesium. Using an environmental SEM, observations were made in vacuum and in the presence of water vapor at 20 Torr. In the vacuum environment, fatigue cracks in the magnesium formed preferentially at pores, sometimes precluded by observable cyclic slip accumulation. At higher cycle numbers in the vacuum environment, additional cracks were discovered to initiate at persistent slip bands within relatively large magnesium dendrite cells. The propagation behavior of small fatigue cracks (a ‹ 6–10 dendrite cells) was found to depend strongly on both environment and microstructure. Small fatigue cracks in the magnesium cycled under vacuum were discovered to propagate along interdendritic regions, along crystallographic planes, and through the dendrite cells. The preference to choose a given path is driven by the presence of microporosity, persistent slip bands, and slip incompatibilities between adjacent dendrite cells. Fatigue cracks formed more rapidly at certain locations in the water vapor environment compared to the vacuum environment, leading to a smaller total number of cracks in the water vapor environment. The majority of small cracks in magnesium cycled in the water vapor environment propagated straight through the dendrite cells, at a faster rate than the cracks in the vacuum. In the water vapor environment, cracks were observed to grow less frequently through interdendritic regions, even in the presence of microporosity, and cracks did not grow via persistent slip bands. The propagation behavior of slightly larger fatigue cracks (a › 6–10 dendrite cells) was found to be Mode I-dominated in both environments.

Document Type:Article
Title:In-situ observations of high cycle fatigue mechanisms in cast AM60B magnesium in vacuum and water vapor environments
Authors:
AuthorsInstitution or Email of Authors
Gall, KenUniversity of Colorado
Biallas, GerhardUNSPECIFIED
Maier, Hans JürgenUniversität Paderborn
Gullett, PhilSandia National Laboratories
Horstemeyer, Mark F.Sandia National Laboratories
McDowell, David L.Georgia Institute of Technology
Fan, JinghongAlfred University
Date:2004
Journal or Publication Title:International Journal of Fatigue
Refereed publication:Yes
In ISI Web of Science:Yes
Volume:26
Page Range:pp. 59-70
Status:Published
Keywords:cast magnesium, in-situ fatigue, small cracks, environmental degradation, surface layer, hydrogen embrittlement, damage mechanisms
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Aeronautics
HGF - Program Themes:Aircraft Research
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Structures & Materials
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Research > Mechanical Testing of Materials
Deposited By: Dr.-Ing. Gerhard Biallas
Deposited On:27 Jan 2006
Last Modified:27 Apr 2009 04:55

Repository Staff Only: item control page

Browse
Search
Help & Contact
Informationen
electronic library is running on EPrints 3.3.12
Copyright © 2008-2012 German Aerospace Center (DLR). All rights reserved.