TY - JOUR

T1 - Enhanced dissimilar aluminum alloy joints using 0.1 mm offset in refill friction stir spot welding

AU - Maranho, José Francisco Caldeira

AU - Cui, Fan

AU - Tang, Huawei

AU - Feng, Xiaosong

AU - Luan, Hao

AU - Shen, Junjun

AU - Wolf, Witor

AU - Freitas, Brenda Juliet Martins

AU - Li, Wenya

AU - Alcântara, Nelson Guedes de

AU - Santos, Jorge Fernandez dos

AU - Klusemann, Benjamin

AU - Koga, Guilherme Yuuki

PY - 2025/5

Y1 - 2025/5

N2 - 5A06-O and 2219-T87 aluminum alloys are promising candidates for propellant tanks. In this study, refill friction stir spot welding (refill FSSW) with a 0.1 mm offset was applied to produce defect-free 5A06-O/2219-T87 welds. A Box-Behnken method and statistical analysis were used to optimize the processing parameters, by determining the influence of welding parameters on lap shear strength (LSS). Plunge depth was the most influential parameter on LSS. All joints failed through the weld seam, including those tested at −55 °C. Microhardness measurements showed a slight increase in the 5A06 sheet over time, while the 2219 sheet exhibited significant hardness reduction. Microstructural analysis revealed typical features of refill FSSW, including a heat-affected zone, thermo-mechanically affected zone, stir zone, hook, and joint-line remnants. Novel findings include the identification of an onion structure in the welds, characterized by fine equiaxed grains and nanoprecipitates that contribute to weld's hardness. This unique microstructure, formed under the thermal and mechanical conditions of the FSSW process, strengthens the material and enhances its mechanical performance. Stop-action tests provided insights into material flow and microstructural evolution during welding. While conventional refill FSSW could not produce defect-free welds, the findings highlight the potential of the 0.1 mm offset refill FSSW to enhance weld quality, supporting its application in aerospace components requiring high mechanical integrity across extreme temperature ranges.

AB - 5A06-O and 2219-T87 aluminum alloys are promising candidates for propellant tanks. In this study, refill friction stir spot welding (refill FSSW) with a 0.1 mm offset was applied to produce defect-free 5A06-O/2219-T87 welds. A Box-Behnken method and statistical analysis were used to optimize the processing parameters, by determining the influence of welding parameters on lap shear strength (LSS). Plunge depth was the most influential parameter on LSS. All joints failed through the weld seam, including those tested at −55 °C. Microhardness measurements showed a slight increase in the 5A06 sheet over time, while the 2219 sheet exhibited significant hardness reduction. Microstructural analysis revealed typical features of refill FSSW, including a heat-affected zone, thermo-mechanically affected zone, stir zone, hook, and joint-line remnants. Novel findings include the identification of an onion structure in the welds, characterized by fine equiaxed grains and nanoprecipitates that contribute to weld's hardness. This unique microstructure, formed under the thermal and mechanical conditions of the FSSW process, strengthens the material and enhances its mechanical performance. Stop-action tests provided insights into material flow and microstructural evolution during welding. While conventional refill FSSW could not produce defect-free welds, the findings highlight the potential of the 0.1 mm offset refill FSSW to enhance weld quality, supporting its application in aerospace components requiring high mechanical integrity across extreme temperature ranges.

KW - Aluminum alloys

KW - 5A06-O

KW - 2219-T87

KW - Joining technologies

KW - Mechanical properties

KW - Engineering

U2 - 10.1016/j.jmrt.2025.03.200

DO - 10.1016/j.jmrt.2025.03.200

M3 - Journal articles

VL - 36

SP - 1091

EP - 1104

JO - Journal of Materials Research and Technology

JF - Journal of Materials Research and Technology

SN - 2238-7854

ER -