Simulation of heat transfer and analysis of impact of tool pin geometry and tool speed during friction stir welding of AZ80A Mg alloy plates

Abstract

Peak temperature arising during the joining of metals by friction stir welding (FSW) needs to be investigated along with other process parameters of FSW to understand their inevitable impact on joint quality. This investigational and experimental analysis aims to determine the impact of pin geometry and its rotational speed by formulating thermic mechanical process-based models to anticipate peak temperature and to compare it with actual values. Three distinctive pin geometries rotated at three speeds were used while other parameters were unchanged. The fitness and suitability of the model were verified by comparing the anticipated values with the experimental values. Macrographic and micrographic observations revealed that flawless joints with improved mechanical properties were fabricated at a peak temperature of 616 K (80 % melting temperature) when a taper cylindrical pin with a rotational speed of 818 rpm was employed. In addition, SEM analysis of the fractured specimen confirmed that failure of the defect free weldment occurred in brittle mode, indicating that preferred fusion of grains and their constituents occurred during the joining process. Compared with other solid-state and unconventional welding techniques, such as electron beam welding, laser beam welding, and plasma arc welding, FSW is cheaper and more cost effective and does not require filler material and shielding medium (or gas), strict safety measures due to the absence of molten spatter and toxic fumes, skilled labor, long operation period, and cool down period, thereby boosting production rate and efficiency; moreover, FSW can be employed to fabricate joints in all positions, including horizontal, vertical, and overhead [12][13][14].

Development of Thermo Mechanical Model for Prediction of Temperature Diffusion in Different FSW Tool Pin Geometries During Joining of AZ80A Mg Alloys

“…This unique transformation of grain structures is a direct evident to the fact that, the ideal peak temperature (ie., 348 0 C which is nearly 81 -82% of the melting temperature of AZ80A Workpiece) has been generated due to the employment of the FSW tool with optimal pin geometry (i.e., taper cylindrical pin geometry). This ideal peak temperature generation have led to superplasticity, which has contributed for plastically deformed material flow in an orderly manner, coupled together with dynamic recyrstallization of the grain structures [18,23,38,47]. Further detailed examination of these microstructures also helps us to understand that, generation of the peak temperature in ideal volumes plays a crucial part in deciding grain size & their refinement.…”

“…Thus, it can be understood that, the technique of FSW joins materials in their solid state itself and due to this reason, it has various added merits like less input of energy, reduced volume of residual stresses, greater strength of weld etc when compared to that of the numerous fusion welding techniques [18,19]. But, inspite of the simple & user friendly principle of joining, there seems to exist various unexplored areas and research complications arising due to the anomalies occurring internal flow of plasticized materials due to the exhilarating action of the FSW tool pin geometry and by the generated heat arising from friction between shoulder and workpiece surface [20][21][22][23] Detailed illustration of the thermo mechanical anomaly occurring between the flat metal plates to be joined and the employed FSW tool pin will enable optimization of welding parameters, perfect design of FSW tool, extending the application of the FSW to various new dimensions [24 -26].…”

Optimization of Friction Stir Welding Operation using Optimal Taguchi-based ANFIS and Genetic Algorithm

“…The empirical models of the TS, EL, and percentage reduction in area were developed in terms of the S, f, and SD for the carbon steel weld [22]. A simulation model was developed to investigate the impacts of the S and pin geometry on the WT for the AZ80A Mg alloy weld, in which the authors stated that the maximum WT was obtained by means of distinctive geometries [23].…”

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

“…Among solid-state joining techniques, Friction Stir Welding (FSW) is a relatively new and useful technique used in various industries such as aerospace, marine, and automotive industries [1][2][3][4]. In the FSW process, a non-consumable rotating tool heats the two pieces due to the contact and intense friction between the two pieces [5][6][7]. Many factors affect the FSW joint, which are classified into two general categories of process parameters and tool geometry [5][6][7].…”

“…In the FSW process, a non-consumable rotating tool heats the two pieces due to the contact and intense friction between the two pieces [5][6][7]. Many factors affect the FSW joint, which are classified into two general categories of process parameters and tool geometry [5][6][7]. 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].…”