# Investigating the Welding Parameters in Friction Stir Welding of Yellow Brass 405-20
## 1 Introduction
Rotational speed, traverse speed, tool pin profile, and welding preheating conditions were optimized to maximize the tensile strength and minimize the tool wear rate. Optimum FSWFs were rotational speed 1500 rpm, welding speed 90 mm/min, tool profile cylindrical, and welding condition (80 \({}^{\circ}\)C preheated) at 5.32 and 1.65% to improve tensile strength and tool wear rate. [PERSON] et al. [22] welded AA6061/TiO\({}_{2}\) composites using the FSW process. Their main emphasis remained on finding the relationships between response parameters that comprise hardness, yield strength, ultimate tensile strength (UTS), and FSWFs. They used the response surface methodology for relating the input variables and output responses. The appropriateness of models was investigated by ANOVA. They also used the teaching-learning based optimization (TLBO) algorithm to attain the optimal levels of FSWF, leading to a welded joint with satisfactory mechanical properties. An FSW joint with UTS of 174 MPa, yield strength of 120 MPa, and hardness of 126 HV was achieved by using TLBO. There was also a close agreement between TLBO and experimental results. [PERSON] et al. [23] performed a multi-objective optimization of AA1050 A-H12 aluminum alloy using the response surface methodology together with a swarm optimization algorithm. However, a research gap still exists, motivating the researchers to perform a thermal numerical study based on FEA to investigate the effect of FSW factors on the thermal distribution at the welded joint and joint strength. The FSWFs utilized were tool pin geometry, rotational speed, welding speed, tool tilt angle, and shoulder diameter. The output responses included the hardness, yield strength, fracture strain, and impact toughness on both advancing and retreating sides. The yield strength and hardness reached their maximum values when keeping the rotational speed lower and the welding speed higher. Likewise, [PERSON] et al. [24] optimized FSWFs that consisted of setting rotational speed, axial force, tool tilt angle, and tapered pin tool pin profile. An extensive empirical optimization study was conducted towards joining AA6061 and AA7075 dissimilar aluminum alloys to enhance the joint quality in terms of its hardness, tensile, and impact strengths. The Taguchi DOE was employed in this study. Rotational speed and tilt angle of the FSW tool were found to be the most significant FSWFs. [PERSON] et al. [25] joined aluminum alloys and ceramics-reinforced aluminum composites using the FSW process. Alumina and silicon carbide were used as ceramic reinforcements. The UTS was optimized usingweighted aggregated sum product assessment (WASPAS). A UTS of AA1000 alloy and AA6061 5% alumina was found to be the highest. Of the WASPAS optimization techniques, AA6061 5% alumina and AA1100 5% alumina were ranked as the best in terms of corrosion resistance. [PERSON] et al. (2016) optimized different combinations of Al-Cu alloys using the Taguchi method to maximize again the UTS. Among the results, a spindle speed of 700 rpm, a transverse speed of 15 mm/min, and D/d ratio of 3 were found as the optimal levels of FSWF. [PERSON] and [PERSON] (2017) optimized aluminum matrix composites (AMCs) with ceramic reinforcement of silicon carbide and silicon nitride. The objective function of the optimization was to maximize the hardness of AMCs. The results showed that optimal FSWF resulted in maximum hardnesses for both composites. However, the hardness of SiC-reinforced AMCs was higher than that of Si3N4-reinforced AMCs. [PERSON] et al. (2018) presented the idea of performing thermal analysis numerically as well as experimentally with aluminum alloys. In their study, weld temperatures and thermal strains were measured while welding aluminum as a function of FSW factors. Although numerical and empirical results agreed, aluminum was again used, which should be replaced with a novel material such as brass. In a similar study on aluminum alloy, [PERSON] et al.