Accession Number : AD1029771

Title :   Characterization of Aluminum Magnesium Alloy Reverse Sensitized via Heat Treatment

Descriptive Note : Technical Report

Corporate Author : Naval Postgraduate School Monterey United States

Personal Author(s) : Gamble,Kevin D

Full Text :

Report Date : 01 Sep 2016

Pagination or Media Count : 83

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 techniques suitability for shipboard repair.

Descriptors :   stress strain relations , stress corrosion , stress corrosion cracking , heat treatment , mechanical working , tensile strength , materials engineering , aluminum oxides , grain boundaries , aluminum alloys , littoral combat ships , mechanical properties

Distribution Statement : APPROVED FOR PUBLIC RELEASE