In this paper, the optimal parameters of the FSW welding process to improve the joint's mechanical properties are obtained using robust multi-objective optimization. First, the properties of the weld zone, such as the chemical composition of the weld, are investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The hardness and tensile properties of the weld were investigated to evaluate the mechanical properties of the joint. The results show at the AA7075 side, the highest hardness is observed in the TMAZ, and the hardness is reduced in the SZ. Tensile testing revealed that the joint's mechanical characteristics were superior to those of the basic metals. In order to obtain the relationship between the process input parameters and the mechanical properties of the obtained joint, an artificial neural network model (ANN) was used. The relationship obtained by ANN was then used to obtain the optimal values of process parameters considering uncertainties in a robust optimization algorithm. In this way, using such an obtained feed-forward neural network and the Monte Carlo simulation, a multi-objective genetic algorithm is used for the robust Pareto optimization of the friction stir welding parameters having probabilistic uncertainties in parameters. Finally, the Technique for Order Preference by Similarity to the Ideal Solution (TOPSIS) was used to get the best optimum solution. The robust optimal process parameters were determined by robust multivariate optimization to be 1467 rpm rotational speed and 11 mm/min traverse velocity. Manuscript profile

In this research, Al-SiC composites were produced using FSP tools with different pin shapes to investigate the distribution of reinforcing particles in the base metal. First, to obtain the optimal rotational and traverse speed and tilt angle, several tests were performed on different parameters. The results showed that the rotational speed of 1250 rpm and the traverse speed of 100 mm/min in all tools produced flawless samples. Then, tools with different tool pin profiles of triflate, cylindrical, threaded, triangular, square, and hexagonal were utilized in this study. The distribution of reinforcing particles in the base metal was studied using a light microscope. The results showed that the cylindrical tool was not able to distribute particles in the base metal even after four passes of the process and was not a suitable tool for composite production. Tools with flat surfaces, such as square and triangular tools, have performed better in distributing reinforcing particles in the base metal. The results showed that the presence of a kind of eccentricity and pulse production in these tools had improved the distribution of particles. Threaded and hexagonal tools have the best performance in the distribution of reinforcing particles in the base metal and can be introduced as a suitable tool for composite products in the FSP process. The results of this study also showed that the change in the direction of tool rotation improved the distribution of reinforcing particles in all tools. Manuscript profile

In this study, the distribution of boron carbide in the stir zone of the FSPed specimens was examined experimentally and numerically about probe shape, including circular, square, and hexagonal shapes. First, composites were created using different tools. Then, using an optical microscope, the microstructural properties of the samples, such as the size and shape of the silicon particles, were examined. To simulate the procedure and further explore particle distribution, the coupled Eulerian-Lagrangian (CEL) method is employed. The tool was also modeled using a Lagrangian formulation while the material was characterized using an Eulerian formulation. The model predicted the changes in strain and temperature in composites created with different probe shapes. The outcome demonstrated that the circular probe was not suitable for the production of composites because it could not disperse particles in the parent alloy. Tools with flat surfaces, such as square and hexagonal tools, have more evenly distributed metal particles. Square probes can be employed in the FSP process to create composites and offer the best performance in terms of reinforcing particle distribution in the metal matrix. Due to the greater distribution of reinforcing particles, the sample made with a square tool had the highest hardness. Using a tool with a square pin improves the average hardness by 8 and 21%, respectively, compared to hexagonal and circular tools. Manuscript profile

Al-Si alloys are widely used in the manufacture of automotive parts such as pistons and cylinders. Although it has desired properties for use in pistons, some microstructural properties of this alloy, such as dendrites or the presence of needle-like silicones, reduce the performance of the parts produced. In this research, to modify the microstructural properties and thus improve the mechanical properties of the alloy, the friction stir processing (FSP) method is used. Also, the effect of process parameters such as rotational and traverse speeds as well as the shape of the pin on the microstructural and mechanical properties of the samples, are studied. The results show that the FSP process improves the microstructural properties of the base metal, and thus improves its mechanical properties. Furthermore, by increasing the rotational speed or decreasing the traverse speed of the tool, the silicon particles become finer, and consequently, the microstructural properties are improved. Manuscript profile

Friction Stir Welding has significantly transformed the metal joining industry, and an innovative variation known as stationary shoulder FSW has emerged. This study aimed to compare various aspects, including force, temperature, and strain, between conventional friction stir welding (CFSW) and stationary shoulder friction stir welding (SSFSW). To accomplish this, the finite element method was employed, utilizing the lagrangian technique to model the welding process. The findings revealed that in SSFSW, the highest temperature was observed in the vicinity of the rotating pin. This was attributed to the absence of a rotating shoulder in SSFSW, which played a major role in heat generation during welding. Moreover, the longitudinal forces on the tool in SSFSW were significantly higher compared to CFSW, approximately ten times greater. In the CFSW process, the affected area showing strain usually forms a basin-shaped pattern. However, in the SSFSW process, the strain distribution is confined within the range of the tool pin. Manuscript profile