Fatigue behavior of friction stir welded AA6061 alloy using brass insert

Aluminum alloys, broadly used in aerospace and automotive, are particularly susceptible to fatigue failures. The grain refinement characteristics can improve the fatigue behavior of aluminum alloys, which can be achieved using friction stir welding (FSW). The primary aim of this study is to examine how incorporating a brass insert influences the fatigue crack growth behavior of AA6061-T6 alloy welded through FSW, comparing welds with and without the insert. Microstructural analysis showed fine recrystallized grains are obtained for both welds. However, welding with the insert exhibited smaller grains. Moreover, robust intermetallics are formed for welding with insert due to the intermixing reaction at FSW temperature, which improves mechanical properties such as hardness and tensile strength. The findings on fatigue indicate that the fatigue resistance of the weld with insert is significantly high, which can be attributed to the increased grain boundaries and development of strong intermetallic compounds, which hindered the crack propagation. Fractographic analysis of the fracture surfaces indicated the presence of striation marks in the weld with the insert, which slowed crack propagation and prolonged fatigue life. The findings suggest real-world applications in industries, where improving the fatigue life and structural reliability of welded aluminum components is critical.