In-depth understanding of material flow behavior and refinement mechanism during bobbin tool friction stir welding

Effect of tool–workpiece interface temperature control on the weld quality of a bobbin-tool friction-stir-welded aluminum alloy

“…Interface temperatures of 465°C or 490°C belonging to each situation must be further analyzed in combination with the tensile and metallographic test results. The analysis results presented above are also consistent with the material flow model for the BT-FSW process simulated by Chu et al [18]. They found that the plastic strain region of the workpiece expanded and that the plastic strain increased with increases in the speed, and when the speed reached 600 rpm, the plastic strain region of the material around the tool suddenly shrank and the plastic strain decreased.…”

“…Some researchers found that the temperature of the AS was higher than that of the RS, while others found that the temperature of the RS was higher than that of the AS. Researchers [2,[16][17][18] who found that the temperature of the RS was higher than that measured for the AS believed that during the welding process, most of the materials accumulated on the RS via plastic flow due to the rotation of the tool, and heat accumulated on the RS also via material flow. On the contrary, researchers [19][20][21][22] who found that the temperature of the AS was higher than that of the RS believed that during the welding process, the heat generated on the AS was greater than that generated on the RS because the relative velocity and shear strain rate of the AS were higher than those of the RS.…”

“…The influence of interface temperature control on the material flow behavior will be further discussed in combination with a theoretical model. According to previous studies, the welding heat during FSW primarily consists of two parts: one is the heat generated by friction between the tool and the workpiece, and the other is the plastic deformation heat generated by the flow stress of the material [18]. The friction heat flux can be expressed as follows:…”

“…The temperature of the RS is higher than that of the AS because of the plastic flow of the material. The high-temperature material from the AS flows to the RS [18]. There are two important factors that affect the plastic flow behavior of the material: the friction coefficient of the contact surface between the workpiece and the tool, 𝜇 𝑓 , and the fluid viscosity of the material, 𝜇.…”

Friction Stir Welding of Different Aluminum-Silicon Alloy Compositions Utilizing Conventional Vertical Milling Machine

“…Friction-Stir Welding (FSW) is a solid-state procedure for welding two plates in which there is relative motion between the tool and workpiece, which creates the heat required for the material of the two edges to join by atomic diffusion [1] and was developed by The Welding Institute (TWI), in 1991 [2]. TWI successfully obtained patents for FSW in Europe, the United States, Japan and Australia while completing a development study demonstrating FSW as a realistic and viable technology for welding aluminum alloys from the 2XXX, 5XXX, and 6XXX series [3], [4].…”