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This paper deals with analysis and comparison of the equivalent plastic strain and temperature fields in the aluminium alloy 2024 T3 (AA2024 T3) welded joint, with macro/microstructure appearance and hardness profile. In the alloys hardened by heat treatment, grain size and particle size of the precipitate are functions of equivalent plastic strain, strain rate and temperature. By analysing the equivalent plastic strain fields and temperature fields it is possible, to some extent, to capture the effect of welding parameters and thermo-mechanical conditions on grain structure, and therefore hardness and strength in the welded joint. A coupled thermo-mechanical model is applied to study the material behaviour during the linear welding stage of friction stir welding. The 3-D finite element model has been created in ABAQUS/EXPLICIT software using the Johnson-Cook material law. The values of thermo-mechanical quantities during the welding stage are obtained from the numerical model and shown as distributions across the joint. The obtained values of these quantities are related to the microstructure of the joint zones and hardness distribution, and this relation is discussed. [ABSTRACT FROM AUTHOR]

The heat generated during friction stir welding process depends on plastic deformation of the material and friction between the tool and the material. In this work, heat generation is analysed with respect to the material velocity around the tool in Al alloy Al2024-T351 plate. The slip rate of the tool relative to the workpiece material is related to the frictional heat generated. The material velocity, on the other hand, is related to the heat generated by plastic deformation. During the welding process, the slippage is the most pronounced on the front part of the tool shoulder. Also, it is higher on the retreating side than on the advancing side. Slip rate in the zone around the tool pin has very low values, almost negligible. In this zone, the heat generation from friction is very low, because the material is in paste-like state and subjected to intensive plastic deformation. The material flow velocity around the pin is higher in the zone around the root of the pin. In the radial direction, this quantity increases from the pin to the periphery of the tool shoulder. [ABSTRACT FROM AUTHOR]

A coupled thermo-mechanical model was developed to study the temperature fields, the plunge force and the plastic deformations of Al alloy 2024-T351 under different rotating speed: 350, 400, and 450 rpm, during the friction stir welding process. 3-D FE model has been developed in ABAQUS/Explicit using the arbitrary Lagrangian-Eulerian formulation, the Johnson-Cook material law, and the Coulomb's Law of friction. Numerical results indicate that the maximum temperature in the friction stir welding process is lower than the melting point of the welding material. The temperature filed is approximately symmetrical along the welding line. A lower plastic strain region can be found near the welding tool in the trailing side on the bottom surface. With increasing rotation speed, the low plastic strain region is reduced. When the rotational speed is increased, the plunge force can be reduced. Regions with high equivalent plastic strains are observed which correspond to the nugget and the flow arm. [ABSTRACT FROM AUTHOR]