Optimization of process parameters to maximize ultimate tensile strength of friction stir welded dissimilar aluminum alloys using response surface methodology

Aluminium alloys generally present low weldability by traditional fusion welding process. Development of the friction stir welding （FSW） has provided an alternative improved way of producing aluminium joints in a faster and reliable manner. The quality of a weld joint is stalwartly influenced by process parameter used during welding. An approach to develop a mathematical model was studied for predicting and optimizing the process parameters of dissimilar aluminum alloy （AA6351 T6-AA5083 Hlll）joints by incorporating the FSW process parameters such as tool pin profile, tool rotational speed welding speed and axial force. The effects of the FSW process parameters on the ultimate tensile strength （UTS） of friction welded dissimilar joints were discussed. Optimization was carried out to maximize the UTS using response surface methodology （RSM） and the identified optimum FSW welding parameters were reported.

Base material location dependence of corrosion response in friction-stir-welded dissimilar 2024-to-5083 aluminum alloy joints

The effects of the base material(BM)location on the mechanical properties and the exfoliation corrosion performance of friction-stir-welded(FSWed)dissimilar 2024-to-5083 aluminum alloy joints were investigated.Scanning electron microscopy(SEM),electron backscatter diffraction(EBSD),transmission electron microscopy(TEM),tensile tests and electrochemical experiments were conducted.The results revealed that the BM location had little effect on the tensile properties of the joints.The grain orientation spread(GOS)value of 2024 alloy side was lower than that of 5083 alloy side.Intergranular corrosion occurred mainly on the 2024 alloy side,while the grain interior of the 5083 alloy side was corroded due to the higher GOS value and dislocation density.The FSWed dissimilar joints with a superior exfoliation corrosion resistance could be achieved when the 5083 aluminum alloy with better corrosion performance was positioned on the retreating side.

Effect of Sheet Configuration on Microstructure and Mechanical Behaviors of Dissimilar Al–Mg–Si/Al–Zn–Mg Aluminum Alloys Friction Stir Welding Joints

Friction stir welding（FSW） was used to weld dissimilar Al-Mg-Si/Al-Zn-Mg aluminum alloys in this work.Influences of sheet configuration on microstructure and mechanical properties of the joints were mainly discussed.Results showed that rather different joint cross sections were obtained when using different sheet configurations.Coarser β＇ phases can be observed at the heat affected zone（HAZ） of the Al-Mg-Si alloy side,which was the main factor affecting the tensile properties and the fatigue properties.Tensile strengths of the dissimilar Al-Mg-Si/Al-Zn-Mg joints using both configurations were higher than that of the Al-Mg-Si FSW joint.When the Al-Zn-Mg alloy was located at the advancing side（AS）,the joints owned better fatigue properties due to the bridging effect of the big secondary phase particles.

Tensile and cyclic deformation response of friction-stir-welded dissimilar aluminum alloy joints:Strain localization effect

Cyclic deformation behavior of friction-stir-welded dissimilar AA2024-T351 to AA7075-T65 aluminum alloy joints was evaluated via stepwise tests at different strain rates,along with transmission electron microscopy examinations to characterize the precipitates required to assess internal stresses.Electron backscatter diffraction was employed to observe the inhomogeneous microstructures of the FSWed joints.Strain localization appeared in the heat affected zone(HAZ)of AA2024 side.After cyclic deformation of 500 cycles at a total strain amplitude of 0.5%,the strength of the dissimilar joints resumed basically to that of AA2024 base material.And the AA2024 HAZ was obviously hardened,which should be attributed to the introduced dislocations during cyclic deformation process.Cyclic hardening capacity of the joints increased with decreasing strain rate.

Assessing the Bonding Interface Characteristics and Mechanical Properties of Bobbin Tool Friction Stir Welded Dissimilar Aluminum Alloy Joints

This study focuses on the bonding interface characteristics and mechanical properties of the bobbin tool friction stir welded dissimilar AA6056 and AA2219 aluminum alloy joints using diff erent welding speeds.Voids arise solely in the stir zone at the AA2219 side.A distinct boundary with limited material mixing develops at the middle section of the bonding interface,while excellent material mixing with an irregularly jagged pattern forms at the top and bottom sections of the bonding interface.Increasing the welding speed,the material mixing is rarely changed at the middle section in comparison with the bottom section.Furthermore,a small diff erence between Guinier–Preston dissolution and Q phase precipitation leads to rare change of hardness in the heat aff ected zone(HAZ)at the AA6056 side.The increased hardness of the HAZ at the AA2219 side is attributed to avoidance of the dissolution ofθ’’phase precipitates.A maximum tensile strength of 181 MPa is obtained at 300 mm min-1.Fractures occur at the AA6056 side near the top and bottom surfaces and at the bonding interface in the middle section of the joints.The regions close to the top and bottom surfaces of the joints show a better ductility.

Microstructure and Mechanical Properties of Pulse MIG Welded 6061/A356 Aluminum Alloy Dissimilar Butt Joints

The microstructure and mechanical properties of pulse metal inert-gas （MIG） welded dissimilar joints between 4 mm thick wrought 6061-T6 and cast A356-T6 aluminum alloy plates were investigated. The tensile strength of the joints reached 235 MPa, which is 83% of that of 6061 aluminum alloy, and then decreased with the increase of travel speed while keeping other welding parameters constant. The microstructure, composition and fractography of joints were examined by the optical microscopy （OM）, scanning electron microscopy （SEM） and electron probe microanalysis （EPMA）. Grain boundary liquation and segregation occurred in the partially melted zone （PMZ） on 6061 aluminum alloy side, and brittle Fe-rich phases were observed in partially melted zone on A356 aluminum alloy side. The minimum microhardness appeared in heat-affected zone （HAZ） near A356 aluminum alloy substrate. The samples during tensile test failed mainly in PMZ and HAZ on A356 aluminum alloy side through mixed fracture mode with quasi cleavage and dimples on fracture surface.