Abstract
In this study, the welding thermal simulation technology was used to prepare samples under different peak temperatures and strain levels in order to reveal the effects of thermal strain on the microstructure characteristics and corrosion resistance of aluminum alloy. Furthermore, the correlation between microstructure evolution law and corrosion behavior was studied by analyzing the microstructure characteristics and performing electrochemical polarization curve tests. Results showed that the amount and distribution of the precipitated phase were the main factors affecting the corrosion behavior of aluminum alloy. The precipitated phase was distributed along the direction of tensile strain, and the grain size was coarsened from 152 to 260 μm (and even exceeded 280 μm) after experiencing peak temperatures of 300 and 400 °C. In addition, the risk of corrosion for the samples that experienced thermal strain was increased compared to those that did not undergo tensile strain. The samples that experienced a peak temperature of 300 °C presented the best corrosion resistance as the precipitated phase was evenly distributed in the matrix. However, when the peak temperature was 400 °C and the strain was 8%, the number and density of the precipitated phase increased due to the dynamic recrystallization, and the corrosion resistance of the sample became the worst. Finally, the microstructure analysis results showed that dynamic recrystallization occurred in the sample with a peak temperature of 400 °C, and the precipitated phase was mainly distributed along the grain boundaries. This led to the decrease of the corrosion resistance of grain boundaries, and the corrosion developed from pitting corrosion to intergranular corrosion.
Highlights
With the development of the manufacturing industry, aluminum alloy has become one of the most commonly used materials in this field
Friction stir welding (FSW), a new solid phase welding technology, has the advantages of environmental protection, high efficiency, excellent performance of welded joints, etc., and is a common welding method used in processing the 2A12 aluminum alloy [8,9,10]
°C; (d) 8% was pre-strain given at peak temperature pre-strain given was at peak temperature of 400 ◦ C. of 400 °C
Summary
With the development of the manufacturing industry, aluminum alloy has become one of the most commonly used materials in this field. Friction stir welding (FSW), a new solid phase welding technology, has the advantages of environmental protection, high efficiency, excellent performance of welded joints, etc., and is a common welding method used in processing the 2A12 aluminum alloy [8,9,10] This aluminum alloy structure is highly sensitive to the effects of marine atmosphere, humid air, and other corrosive elements in the environment, which in turn, lead to corrosion-induced problems, such as pitting corrosion, intergranular corrosion or exfoliation corrosion. Wang et al [16] explored the stress corrosion sensitivity of 2024-T3 aluminum alloy FSW joint, and concluded that the main reason influencing the stress corrosion sensitivity was that the size of the precipitated phase particles increased due to thermal cycling, which in turn, led to pitting corrosion expansion, leading to stress corrosion. The findings of this study can be used to provide the theoretical basis for the optimization of FSW parameters
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