Dissimilar Friction Stir Welds in AA2219-AA5083 Aluminium Alloys: Effect of Process Parameters on Material Inter-Mixing, Defect Formation, and Mechanical Properties

Abstract

Dissimilar friction stir welds of aluminium alloys AA 5083 and AA2219 were investigated in a view to get defect free welds by varying process parameters. An attempt has been made to develop a mathematical model to predict sound welds. Design of experiments with three parameters and five levels were used to optimize the effectiveness of process parameters. Analysis of variance and response surface methodology were used to determine the significance and optimal level for each parameter to minimize % area of volumetric defect. The experimental and predicted values of % area of defect were in good agreement. The effects of process parameters and tool-offset on the extent of intermixing of materials and to minimize % area of volumetric defects are analyzed in detail by employing different methods such as macrostructural analysis and electron probe micro analysis. The defect free dissimilar weldments were characterized for transverse tensile properties. The observed tensile strength values were correlated with reference to the extent of intermixing of materials in the stir/nugget zone. Established mathematical models which have depicted a good prediction of relationship between the investigated FSW process parameters and the % area of defect of the welds. It is understood # Co-corresponding Author ## Corresponding Author that the mixing pattern in nugget zone and further joint strength are primarily affected by the tool offset and welding parameters.

Friction Stir Welding of Dissimilar Aluminum Alloy Combinations: State-of-the-Art

“…Kalemba-Rec et al [16] showed a proportional relationship between material mixing and tool rotation speed for a dissimilar AA7075-AA5083 joint. However, very large rotation speeds lead to numerous imperfections such as poor surface (flash), voids, porosity, tunneling or formation of wormholes because of the excessive heat input [75][76][77], as shown In the case of the lap joint, the BM placement affects the material flow and leads to the generatio the ubiquitous hook defect. Now the material movement is in an upward direction that is, from bottom sheet to the top sheet, creating hook defects of various sizes.…”

“…Kalemba-Rec et al [16] showed a proportional relationship between material mixing and tool rotation speed for a dissimilar AA7075-AA5083 joint. However, very large rotation speeds lead to numerous imperfections such as poor surface (flash), voids, porosity, tunneling or formation of wormholes because of the excessive heat input [75][76][77], as shown in Figure 7. Low welding speeds increase heat input and are associated with defects like tunneling [55,58,75,78,79].…”

“…However, very large rotation speeds lead to numerous imperfections such as poor surface (flash), voids, porosity, tunneling or formation of wormholes because of the excessive heat input [75][76][77], as shown in Figure 7. Low welding speeds increase heat input and are associated with defects like tunneling [55,58,75,78,79]. It is therefore necessary to select the appropriate combination of tool rotation and welding speed for a defect free joint with a good metallurgical bond and mechanical properties.…”

Developments of mathematical models for prediction of tensile properties of dissimilar AA6061-T6 to Cu welds prepared by friction stir welding process using Zn interlayer

“…Including three repeat runs for the central points (for which all factors are kept at their intermediate levels; coded value: 0) makes a total of 15 runs [31]. Applications of response surface methodology for investigating effects of friction stir welding process parameters on tensile properties or other responses have been reported in the literature [32][33][34][35]. Ghetiya and Patel [32] developed a mathematical model for prediction of tensile strength of AA2014-T4 immersed friction stir welds using Box-Behnken design.…”

Effect of tool geometry and welding speed on mechanical properties of dissimilar AA2198–AA2024 FSWed joint

“…A low rotational speed or a higher traverse speed cause tunneling defect and kissing bond due to insufficient material mixing as the heat input is too low and the material is not soft enough [27]. On the other hand, a combination of high speeds and high traverse speeds causes cavities due to abnormal stirring [28]. In the range of optimized welding parameters, increasing the traverse speed in the presence of a constant rotational speed improves joint mechanical properties [29], while increasing the rotational speed results in higher heat input and lower mechanical properties [30].…”