Effect of friction spot welding (FSpW) on the surface corrosion behavior of overlapping AA6181-T4/Ti-6Al-4V joints

• Published in: Materials & design Vol. 131; pp. 127 - 134
• Main Authors: Vacchi, G.S., Plaine, A.H., Silva, R., Sordi, V.L., Suhuddin, U.F.H., Alcântara, N.G., Kuri, S.E., Rovere, C.A.D.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 05-10-2017
• Subjects: Dissimilar joint, aluminum alloys; Friction spot welding; FSpW; Hardness; Pitting corrosion; Pitting corrosion; Hardness; FSpW; Friction spot welding; Dissimilar joint, aluminum alloys
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2017.06.005

The microstructural, mechanical and corrosion behavior of the surface of an AA6181-T4 aluminum alloy overlap welded onto Ti-6Al-4V titanium alloy by friction spot welding (FSpW) was analyzed based on optical microscopy (OM), scanning electron microscopy (SEM), microhardness and potentiodynamic polarization techniques. The results indicated that the FSpW process modified the microstructure of the AA6181-T4 aluminum alloy, as indicated mainly by the size, type and quantity of precipitates in various welding regions. The microhardness tests showed similar hardness values in the stir zone (SZ) and base metal (BM), which was ascribed to the breakdown and homogenization of precipitates in the SZ. On the other hand, the heat affected zone (HAZ) showed the lowest hardness, which was attributed to the coalescence of Mg2Si precipitates caused by the thermal cycle of the welding process. The potentiodynamic polarization tests indicated that the SZ showed the highest pitting potential due to the refined microstructure in this zone. SEM images recorded after potentiodynamic polarization testing indicated that preferential sites for pitting nucleation were regions adjacent to the Al (Fe, Si, Mn, Mg) precipitates, and the mildest corrosive attack was found in the SZ.
[Display omitted]
•The corrosion resistance of the aluminum surface of FSp welded dissimilar joints was investigated.•The HAZ showed the lowest hardness.•FSpW process promoted the breakdown of precipitates in the SZ.•The microstructural changes triggered by FSpW increased the pitting resistance in the SZ.•Pitting occurred preferentially in the region surrounding the precipitates.