Improve sensitization and corrosion resistance of an Al-Mg alloy by optimization of grain boundaries.

Jianfeng Yan,Andrea M Hodge,Nathan M Heckman,Leonardo Velasco

doi:10.1038/srep26870

Jianfeng Yan, Andrea M Hodge + Show 2 more

Open Access

https://doi.org/10.1038/srep26870

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Journal: Scientific Reports	Publication Date: May 27, 2016
Citations: 51	License type: CC BY 4.0

Affiliation: University of Southern California

Abstract

The sensitization and subsequent intergranular corrosion of Al-5.3 wt.% Mg alloy has been shown to be an important factor in stress corrosion cracking of Al-Mg alloys. Understanding sensitization requires the review of grain boundary character on the precipitation process which can assist in developing and designing alloys with improved corrosion resistance. This study shows that the degree of precipitation in Al-Mg alloy is dependent on grain boundary misorientation angle, adjacent grain boundary planes and grain boundary types. The results show that the misorientation angle is the most important factor influencing precipitation in grain boundaries of the Al-Mg alloy. Low angle grain boundaries (≤15°) have better immunity to precipitation and grain boundary acid attack. High angle grain boundaries (>15°) are vulnerable to grain boundary acid attack. Grain boundaries with adjacent plane orientations near to {100} have potential for immunity to precipitation and grain boundary acid attack. This work shows that low Σ (Σ ≤ 29) coincident site lattice (CSL) grain boundaries have thinner β precipitates. Modified nitric acid mass loss test and polarization test demonstrated that the global corrosion resistance of sputtered Al-Mg alloy is enhanced. This may be attributed to the increased fractions of low Σ (Σ ≤ 29) CSL grain boundaries after sputtering.

Highlights

The sensitization and subsequent intergranular corrosion of Al-5.3 wt.% Mg alloy has been shown to be an important factor in stress corrosion cracking of Al-Mg alloys
Zhao et al demonstrated that some low angle grain boundary (GB) can have βprecipitation while some high angle GBs are immune to βprecipitation[22], which is in agreement with the Scotto D’Antuono et al.[21 ], but in contrast to Davemport et al.[23]
The precipitation of a total of 56 GBs in sensitized received Al-Mg alloy was evaluated by acid etching method using conventional electron backscatter diffraction (EBSD) and Scanning electron microscopy (SEM) methods

Summary

Introduction

The sensitization and subsequent intergranular corrosion of Al-5.3 wt.% Mg alloy has been shown to be an important factor in stress corrosion cracking of Al-Mg alloys. Modified nitric acid mass loss test and polarization test demonstrated that the global corrosion resistance of sputtered Al-Mg alloy is enhanced This may be attributed to the increased fractions of low Σ (Σ ≤ 29) CSL grain boundaries after sputtering. Low angle boundaries (

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