Advances in simulation and experimental study on intermetallic formation and thermomechanical evolution of Al–Cu composite with Zn interlayer: Effect of spot pass and shoulder diameter during the pinless friction stir spot welding process

Abstract

In this study, the pinless friction stir spot welding of aluminum–copper composite with Zn interlayer was analyzed under experimental measurement and finite element method. The role of shoulder diameter, 16, 18, and 20 mm, and the number of spot pass, one to three pass, on microstructure, mechanical properties, and thermal history of weld samples were investigated. Based on the obtained results, there is a good agreement between numerical data and experimental analyses. It was shown that the heat source, due to plastic deformation and friction, increased as the shoulder diameter was increased, whereas the stress distribution in the weld samples was reduced. In addition, the thickness of the Zn interlayer at the joint interface changes when shoulder size increases from 16 to 20 mm, due to high temperature and intermixing between materials. From the microstructure analysis, the grain size in the joint zone gradually decreases as the spot pass increases from 1 to 3. It was concluded that the shoulder diameter of 16 mm with three spot passes showed the best result of 7.45 kN. Depending on X-ray diffraction analyses of the fracture surfaces, three primarily intermetallic phases including the Al2Cu, CuZn5, and CuZn2 were determined in the weld interfaces. Based on finite element method analysis, the axial compressive stresses showed the lowest profile as the shoulder diameter of the tool is 16 mm. Finally, the ductile fracture was detected as the main fracture mechanism for the joint sample with optimal joining conditions.

Thermo-Mechanical Study of TIG Welding of Ti-6Al-4V for Residual Stresses Considering Solid State Phase Transformation

“…where f β→α represents the phase fraction of the α phase transformed from the β phase when the temperature is T 2 during the cooling process; K β→α and n β→α represent the temperature-dependent and independent JMAK parameters that determine the kinetics of the β phase; f eq α represent the equilibrium fraction of the α phase. When the peak value of the heating temperature reaches above the transition temperature of the β phase and the cooling rate is between 20 • C/s and 410 • C/s during the cooling process, there would be partial transformation of β phase to grain boundary α G phase and α ′ phase adjacent to the prior-β grain boundary, and it was assumed that α m includes both α G and α ′ and also that both transformations are diffusional and diffusionless [18]. Then, the transformation of β phase to α m phase during the cooling process could be expressed as Equation (6).…”

“…Based on the Taguchi method, Bagheri et al [17] investigated the optimal process parameters of AA6061-T6 aluminum alloy FSW and implemented simulation by a coupled Eulerian and Lagrangian technique, finding that the application of optimal joining conditions can decrease the peak tensile residual stress by about 38.3%. Abdollahzadeh et al [18] analyzed the pinless friction stir spot welding of aluminum-copper composite with Zn interlayer under experimental measurement and the finite element method, and the research results indicated that the heat source, due to plastic deformation and friction, increased as the shoulder diameter was increased, whereas the stress distribution in the weld samples was reduced. Furthermore, they also observed that the axial compressive stresses showed the lowest profile as the shoulder diameter of the tool is 16 mm.…”

Fatigue crack initiation life prediction using different plasticity models in cold expanded AL-alloy plates utilized in double shear lap joints

“…Due to their advantageous properties of ductility and lightweight, aluminum alloys are indispensable elements in aerospace, transportation, and electrical industries and have numerous industrial applications. [1][2][3] Mechanical detachable joints, including riveted, pinned, and bolted joints, have found extensive applications in a wide range of construction projects, notably in the aerospace manufacturing sector. Moreover, these joints represent the fatigue crack sites due to the concentration of stress on the hole edge.…”