Friction Stir Welding of AZ31 Magnesium Alloys - A Numerical and Experimental Study

Abstract

In this paper, weldability of magnesium alloys by friction stir welding (FSW) method which is difficult to join by the fusion welding have been investigated experimentally and numerically. To this end, the connection of magnesium alloys was performed using different welding parameters. AZ31 Mg-alloy plates were friction stir welded at rotation speed of 1200 rev/min and translational speeds of 80,100,120,140 mm/min. Temperature evolution in the weld zone during welding was measured by using embedded K-type thermocouples. The temperature measurements on both advancing and retreading sides were performed by ten thermocouples. Tensile and Vickers hardness tests were conducted to evaluate the mechanical properties and the hardness distribution on the weld, respectively. During FSW, heat is generated by the friction and plastic deformation. Knowledge of the temperature distribution is requisite since mechanical properties and microstructure are substantially affected by the heat generation. It was observed that the heat generated during the FSW process was increasing and the grain structure was refined as the translational speed was decreasing. In the finite element analyses, modeling of the FSW process were carried out by ANSYS software to determine the temperature and stress distributions in the welded joint during FSW. An APDL (ANSYS Parametric Design Language) code was developed to simulate FSW process. Transient nonlinear finite element analyses were performed at two stages which the first step is thermal analysis which heat transfer from the pin and shoulder to the plates was modeled and the second is the structural analysis which the temperature data obtained from the thermal analysis in the first stage is used.

Effects of post-weld heat treatment on the microstructural evolution and mechanical properties of dissimilar friction stir welded AA6061+SiCp/AA6061-O joint

“…By the way, it should be noted once again that the friction and plastic deformation play a significant role on the generated heat during the process. Besides, it is widely accepted that the microstructure and mechanical features of joint are considerably influenced by the generated heat (Serindag and Kiral 2017). It has been reported that the tool rotational speed has more influence on the frictional energy by comparison with other major FSW parameters such as the axial plunge force and welding speed (Aziz et al 2016).…”

Refined Microstructure and Enhanced Hardness in Friction Stir-Welded AZ31 Magnesium Alloy Induced by Heat Pipe with Different Cooling Liquid

“…While the peak values measured at R 1 , R 3 and R 5 are 289 • C, 333 • C, 375 • C. Such a temperature field is commonly found during the FSW process [23,[38][39][40][41]. The distinctions of the peak temperature along the welding direction (WD) are even still presented when the heat pipe is applied in the FSW process, as well as the differences of the temperatures along the transverse direction (the direction perpendicular to the welding direction on the welded plates, which is often abbreviated as TD) [42]. The larger heat loss and unstable generated heat at the beginning of the welding restrict the temperature rising (such as A 1 and R 1 ) [43].…”

Stress Analysis of Friction Stir Spot Welded Magnesium Alloy Sheet under Tensile-Shear Load

“…Using the design principle shown in Figure 1, which is commonly used for the simplest sizing, spot-welding design can be generated as given by equation 1[1] based on the mean shear stress ( ) [3]. A few earlier research reported on the stress mechanisms at the overlapped joints [2][3][4][5][6][7][8][9][10][11][12]. Shen Z. have been investigated AA7075-T6 Aluminum sheet with a mean yield value of 500 MPa and the intended result was achieved only for elastic-elastic analysis.…”

“…Transient nonlinear finite element analyses were performed to make structural stress analysis. It has seen that the welding performance increases as both low transverse speed and high rotational speed increase [7]. In that study, nonlinear ultimate stress analysis has been performed with nonlinear material information.…”

“…Failure modes seen in Tension-shear test are as follows: a) Failure from welding circumferentially, b) Tear by pulling out from nugget, c) Failure by pulling out from upper sheet, d) Failure by pulling out from the lower sheet, e) Failure from all pieces[7] …”