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This research aims to construct a three-dimensional numerical model for modeling friction stir extrusion using the completely Lagrangian method, smoothed particle hydrodynamics (SPH). For extrusion simulations, the Finite Element Method (FEM) is extensively utilized; however, it has limitations due to excessive element deformation. Because the particle-based method eliminates the usage of volumetric elements, SPH can be a viable alternative. The performance of the SPH model was evaluated using different particle sizes. The results showed that the smaller particle size improves the temperature results as well as the shape of the wire produced. Then the mechanical and microstructural properties of the produced wires were investigated. The results show that the grain size in the center of the wire is larger than its perimeter due to the lower strain rate in this area. Increased strain reduces grain size in the produced microstructure by increasing nucleation sites during recrystallization, as is well known. The wire microhardness in the centre is 121 HV, whereas it is 129 HV in the periphery. Grain size is the main reason of increased hardness near the sample's periphery. [ABSTRACT FROM AUTHOR]

In the present work, the effects of in-process cooling are investigated on the material flow, temperature distribution, axial force, wear resistance, and microstructural and mechanical properties of friction stir processed (FSPed) Al-Si aluminum alloy. The finite element method (FEM) was developed for modeling the process, based on the eulerian-lagrangian technique, and then verified by the experimental force and temperature histories. Next, the material flow and temperature distribution during the friction stir process (FSP) with in-process cooling under different conditions were considered. After that, the experimental investigations, including the optical microscopy, hardness, and wear tests, were conducted. Finally, the stir zone (SZ) shape obtained by experiments and simulation model were compared for the FSPed samples without cooling and with air cooling. The material flow achievements reveal that using a coolant affects the material flow in the pin-driven zone more significantly than in the shoulder-driven zone, leading the SZ to change from the basin shape into the V shape. The SZ shapes obtained from the experiments and the simulation model show a good agreement between the shapes of the samples FSPed without cooling and with air cooling. Moreover, experimental results showed that using in-process cooling reduces Si particles' size and thus significantly increases the hardness and wear resistance. The Si particles size is reduced from 10 μm in the base metal to 2.6 μm and 2 μm in the air-cooled and water-cooled samples. Consequently, the wear mass loss reduced almost 28% and 40%, and hardness increased almost 35% and 80% for the air-cooled and water-cooled samples compared to the processed samples without coolant. [ABSTRACT FROM AUTHOR]

Multi-walled carbon nanotube/aluminum composites are fabricated on Al–Si cast alloy employing friction stir processing. First, the microstructure of the stir zone, as well as the effect of process parameters on the size of silicon particles, is investigated. Then, the process is numerically simulated using a thermo-mechanically coupled three-dimensional finite element method model. Material flow, as the primary reason for the dispersion of reinforcing particles, is considered in the numerical model, and proper conditions to obtain a uniform dispersion of multi-walled carbon nanotubes are determined. Scanning electron microscope analysis is carried out to consider the particle distribution in the texture of the stir zone. The results show that the particle distribution improves significantly by changing the tool rotation direction between the friction stir processing passes. The hardness test is accomplished on the cross-section of the friction stir processed specimens, and finally, the wear test is performed to compare the wear resistance of the composites with the base alloy. The results show that the wear resistance and hardness of the produced composites are considerably enhanced compared to the base alloy. [ABSTRACT FROM AUTHOR]

The welding tool parameters play a critical role in obtaining weld strength during friction stir welding. In this investigation, the effect of welding tool parameters such as pin and shoulder diameter and pin height on the axial and traverse forces and also temperature of welding of AA5083 alloy was investigated. A specially designed dynamometer was used to measure the welding tool forces. Then, the mechanical properties of the welds were characterized using tensile tests. Moreover, macrostructure of welds was investigated in order to analyze weld quality. Finally, optimum values for shoulder diameter, pin height and pin diameter were determined. [ABSTRACT FROM AUTHOR]