Correlation between Microstructures and Tensile Properties in Friction Stir Welding Joint of Zn-Modified 5083 Al Alloy

Various Zn contents were utilized as an alloy element adding in the AA5083 aluminum alloys to optimize the properties. The subsequent characterizing techniques show that the hardness distribution of the friction stir welding (FSW) joint is ‘W’ shaped with the nugget zone relatively high, and the hardness of the thermo-mechanical affected zone (TMAZ) being the lowest. The joint with rotation speed of 600 rpm has the best mechanical properties and no welding defects appear. The grain deformation of the TMAZ is greater under the action of the welding tool and grain growth occurs in the heat affected zone (HAZ). Based on slow strain rate testing (SSRT), the FSW joint of the AA5083 alloy containing Zn 0.50 wt.% showed the highest resistance to stress corrosion cracking (SCC), which is probably due to the formation of Zn phase in place of the β (Al3Mg2) phase during welding.