Effects of FSW Tool Plunge Depth on Properties of an Al-Mg-Si Alloy T-Joint: Thermomechanical Modeling and Experimental Evaluation

Abstract

One of the main challenging issues in friction stir welding (FSW) of stiffened structures is maximizing skin and flange mixing. Among the various parameters in FSW that can affect the quality of mixing between skin and flange is tool plunge depth (TPD). In this research, the effects of TPD during FSW of an Al-Mg-Si alloy T-joint are investigated. The computational fluid dynamics (CFD) method can help understand TPD effects on FSW of the T-joint structure. For this reason, the CFD method is employed in the simulation of heat generation, heat distribution, material flow, and defect formation during welding processes at various TPD. CFD is a powerful method that can simulate phenomena during the mixing of flange and skin that are hard to assess experimentally. For the evaluation of FSW joints, macrostructure visualization is carried out. Simulation results showed that at higher TPD, more frictional heat is generated and causes the formation of a bigger stir zone. The temperature distribution is antisymmetric to the welding line, and the concentration of heat on the advancing side (AS) is more than the retreating side (RS). Simulation results from viscosity changes and material velocity study on the stir zone indicated that the possibility of the formation of a tunnel defect on the skin–flange interface at the RS is very high. Material flow and defect formation are very sensitive to TPD. Low TPD creates internal defects with incomplete mixing of skin and flange, and high TPD forms surface flash. Higher TPD increases frictional heat and axial force that diminish the mixing of skin and flange in this joint. The optimum TPD was selected due to the best materials flow and final mechanical properties of joints.

Effect of Pin Shape on Thermal History of Aluminum-Steel Friction Stir Welded Joint: Computational Fluid Dynamic Modeling and Validation

“…where u, v and w present the material velocities in the x, y and z directions. With combination Equations ( 2)-( 4), the viscosity of WM can be presented by [1,[56][57][58]:…”

“…The friction stir welding (FSW) process belongs to the group of solid-state joining processes-it enables to provide the appropriate amount of welding activation energy in the form of heat without exceeding the melting point of base materials (unlike fusion processes: arc, plasma, laser and electron beam welding) [1]. This is advantageous because it limits structural transformations and joint properties changes resulting from the crystallization process [2,3].…”

Investigation of Mechanical and Microstructural Properties of Welded Specimens of AA6061-T6 Alloy with Friction Stir Welding and Parallel-Friction Stir Welding Methods

“…By changing the condition of each of the parameters, the heat and material flow distribution in the process change, which ultimately leads to a change in the mechanical quality of the joint [8][9][10][11][12][13]. The most important factors influencing the FSW process are the temperature and the material flow distribution patterns in the welding zone [14][15][16][17][18]. The heat and flow of materials created in the process derive from two factors: welding geometry and tool geometry.…”

“…In the FSW process, two different zones are formed on either side of the weld line [19][20][21][22][23]. The side where the tool pin surface rotation direction and the tool traverse direction have the same vectorial sense is called the Advancing Side (AS), and the side where the tool pin surface rotation direction and the tool traverse direction have the opposite vectorial sense is called the Retreating Side (RS) [11,16,17]. The two regions of the AS and RS have significant differences in the way of heat distribution and plastic flow patterns, which cause significant differences in mechanical and metallurgical quality in these areas [24].…”

Microstructure and Mechanical Properties of Friction Stir Welded 2205 Duplex Stainless Steel Butt Joints

“…To avoid these difficulties, precise control of the weld chemical composition and working temperature are often recommended during the welding process. As a solid-state technique, friction stir welding (FSW) facilities [15,16] have been developed and used extensively to weld ferrous [17][18][19] and nonferrous [20][21][22] alloys in similar [19,23,24] and dissimilar [25][26][27] joints in various industrial applications. The FSW technique is recommended to join 2205 DSS.…”