Effect of Microstructure on the Corrosion Resistance of TIG Welded 1579 Alloy.

Andrey S Gnedenkov,Sergey V Gnedenkov,Dmitry V Mashtalyar,Sergey L Sinebryukhov,Igor M Imshinetskiy,Igor E Vyaliy

doi:10.3390/ma12162615

Abstract

The paper studies microstructure, chemical composition and corrosion activity of the tungsten inert gas welded joint of the Al-Mg-Sc alloy. An intensive corrosion attack of the heat affected zone (HAZ) was found due to precipitation of secondary phases at recrystallized grain boundaries. The ccorrosion process initiated along the boundary of α-Al grains, where a high concentration of anodic (Mg2Si and Mg2Al3) and cathodic phases ((MnFe)Al6) was observed. Increased temperatures during welding led to coalescence of the anodic phases in HAZ. Additionally, HAZ was found to be enriched with hard intermetallic compounds (Mg2Si and (MnFe)Al6). This area had a higher microhardness (930 MPa) compared to base metal (BM, 895 MPa) and fusion zone (FZ, 810 MPa). The volume fraction of secondary phases was 26% in BM, 28% in FZ and 38% in HAZ. The average grain size increased in the following order: (9 ± 3) µm (BM) < (16 ± 3) µm (HAZ) < (21 ± 5) µm (FZ). A plasma electrolytic oxidation (PEO) coating of aluminum-based material was applied to protect the weld from oxidation. The PEO-coating provided a high corrosion protection in the aggressive Cl−-containing environment.

Highlights

Aluminum alloys remain one of the main structural materials for products manufactured by enterprises of various industries e.g.: aerospace, automobile, and marine
After Tungsten inert gas (TIG) welding of aluminum alloys three zones can be revealed in the material structure (Figure 2): base metal (BM), heat affected zone (HAZ) area, where microstructure evolution is a result of thermal treatment, and fusion zone (FZ), where plastic deformation and recrystallization take place
It has been established that HAZ is more sensitive to localized corrosion as compared to the fusion zone and base material

Summary

Introduction

Aluminum alloys remain one of the main structural materials for products manufactured by enterprises of various industries e.g.: aerospace, automobile, and marine. The presence of intermetallic phases with different corrosion potential in the aluminum alloys activates the localized corrosion and accelerates the material degradation [1,2,3,4]. There are works dealt with study the corrosion activity of aluminum-based intermetallic phases [5,6,7,8]. Nowadays in the aerospace industry to increase the fuel efficiency of the product, which has a specific application, the weight reduction is essential, which is realized using alloys welding process. The corrosion behavior of aluminum alloys becomes more complicated after the welding process [10,11,12]

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