Publication:
Characterization of aluminum-magnesium alloy reverse sensitized via heat treatment

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Authors
Gamble, Kevin D.
Subjects
Reverse Sensitizing 5456 Aluminum Alloy
Advisors
Tran, Kim Ngoc
Menon, Sarath
Date of Issue
2016-09
Date
Sep-16
Publisher
Monterey, California: Naval Postgraduate School
Language
Abstract
This research explores a novel repair technique to reverse the sensitization of aluminum magnesium (Al-Mg) alloys. Al-Mg alloys can become sensitized when magnesium comes out of solution as a second phase, Al₃Mg₂, on the grain boundaries, eventually forming a continuous network and increasing susceptibility to intergranular stress corrosion cracking (SCC). Sensitized 5456 Al-Mg alloy samples removed from active Navy ships were metallographically characterized. These were compared to similar samples that were heat treated in order to reverse the sensitization effect. Both of these were also compared to as wrought 5456 aluminum. All samples were also tested for tensile strength and degree of sensitization using the ASTM G67 Nitric Acid Mass Loss Test (NAMLT). Two heat treatment profiles were compared. Both of these profiles successfully reversed the sensitization effect, with similar performance. Heat treatment may have affected the tensile properties and negatively degraded the resulting microstructure by annealing the material. Therefore, more research is necessary to prove this technique's suitability for shipboard repair.
Type
Thesis
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Department
Mechanical and Aerospace Engineering (MAE)
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Distribution Statement
Approved for public release; distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.
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