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. 2023 Sep 1;16(17):6009.
doi: 10.3390/ma16176009.

Microstructure and Corrosion Behavior of Laser-Welded Al-Mn-Zr Alloy for Heat Exchanger

Jeong-Min Lim  1 , Yoon-Sik So  1 , Jung-Gu Kim  1
Affiliations

Microstructure and Corrosion Behavior of Laser-Welded Al-Mn-Zr Alloy for Heat Exchanger

Jeong-Min Lim et al. Materials (Basel). .

Abstract

In this study, an Al-Mn-Zr alloy was designed and its microstructure and corrosion behavior compared after laser welding to that of AA3003. As the results of immersion and electrochemical tests showed, both alloys had a faster corrosion rate in the fusion zone than in the base metal. Laser welding caused interdendritic segregation, and spread the intermetallic compounds (IMCs) evenly throughout in the fusion zone. This increased the micro-galvanic corrosion sites and destabilized the passive film, thus increasing the corrosion rate of the fusion zone. However, Zr in the Al-Mn alloy reduced the size and number of IMCs, and minimized the micro-galvanic corrosion effect. Consequently, Al-Mn-Zr alloy has higher corrosion resistance than AA3003 even after laser welding.

Keywords: aluminum alloy; corrosion; fusion zone; interdendritic segregation; laser welding; micro–galvanic; passive film; zirconium.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Procedure for laser-welded specimen preparation.
Figure 2
Figure 2
Cross-sectional images of laser-welded specimens. AA3003 (a) 50× and (b) 500× (BM/FZ Interface); U3003 (c) 50× and (d) 500× (BM/FZ interface).
Figure 3
Figure 3
SEM images of BM/FZ interface and EPMA element mapping for Fe and Mn of (a) AA3003 and (b) U3003. The same position as the red circle in the SEM image is indicated by a white circle in the mapping image. EDS point analysis results of IMCs in red circles of (c) AA3003 and (d) U3003.
Figure 4
Figure 4
Microstructures of laser-welded specimens. AA3003 (a) BM, (b) FZ, near BM/FZ interface, and (c) FZ, weld center; U3003 (d) BM, (e) FZ, near BM/FZ interface, and (f) FZ, weld center.
Figure 5
Figure 5
The area ratio of IMCs to Al matrix in BM and FZ calculated from SEM images in Figure 4.
Figure 6
Figure 6
Surface and cross-sectional images of specimens after 12 weeks’ immersion test. (a) Surface image of AA3003 and (b) cross-sectional image at the b1–b2. (c) Surface image of U3003 and (d) cross-sectional image at the d1–d2.
Figure 7
Figure 7
Potentiodynamic polarization curves of (a) AA3003 and (b) U3003.
Figure 8
Figure 8
High-magnification images of cross sections of specimens after 12 weeks’ immersion testing. AA3003 (a) BM and (b) FZ; U3003 (c) BM and (d) FZ.
Figure 9
Figure 9
(a) Equivalent circuit to fit the EIS data. EIS Nyquist plots of (b) AA3003 and (c) U3003. Scatter plots are experimental values and line plots are calculated values.
Figure 10
Figure 10
Schematic mechanism of corrosion behavior of laser-welded Al–Mn alloys.
See this image and copyright information in PMC

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