Precipitation-Induced Grain Growth Simulation of Friction-Stir-Welded AA6082-T6
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JMEPEG DOI: 10.1007/s11665-017-2639-1
Precipitation-Induced Grain Growth Simulation of Friction-Stir-Welded AA6082-T6 Q. Wu and Z. Zhang (Submitted July 14, 2016; in revised form January 7, 2017) Friction stir welding of AA6082-T6 with different welding parameters is simulated by computational fluid dynamics model. Monte Carlo method is further used to simulate the grain growth with consideration of the precipitation effects. The comparison with experimental observations can validate the proposed grain growth model with the precipitate effects. Results indicate that the final grain size can be increased by 39.7% in the nugget zone when the volume fraction of precipitation is decreased from 0.8 to 0.2% after welding. Both the grain growth speed and the final grain size on the top surface are higher than the bottom surface. The increase in the welding temperature caused by the increase in the rotation speeds or the axial forces can lead to lower volume fractions of precipitations and then lead to larger grain sizes. Keywords
friction stir welding, grain size, Monte Carlo method, precipitation
1. Introduction As a solid-state welding technique invented by TWI in 1991, friction stir welding (FSW) has many advantages in comparison with the conventional fusion welding techniques such as low temperature, low distortion and no pollution (Ref 1). FSW can be applied to join aluminum, magnesium, titanium alloys and even steels (Ref 2, 3) and has been quickly applied to a wide range of industries (Ref 4). The grain growth is very important for the determination of the friction stir weld quality. So, researches have been focused on the grain structures in friction stir welding. Many experimental works have clarified the relations between final grain structures and service performances of welds. Rajakumar et al. (Ref 5) established an empirical relationship between the postweld grain sizes and tensile strength in friction-stir-welded aluminum alloy. Safarkhanian et al. (Ref 6) investigated the effect of abnormal grain growth on tensile strength of frictionstir-welded aluminum alloys. Sakthivel and Mukhopadhyay (Ref 7) and Cavaliere and Marco (Ref 8) investigated the microstructure and mechanical properties of friction-stir-welded copper and magnesium alloys, respectively. Different welding parameters and tool geometries are also widely investigated for the optimization of final grain structures. Attallah et al. (Ref 9) studied the factors which can influence the microhardness during FSW of AA5251. Attallah and Salem (Ref 10) reported the controlling of abnormal grain growth during FSW. The effects of tool profiles and weld parameters on the microstructure and mechanical properties are investigated by Xu et al.
Q. Wu and Z. Zhang, State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, Dalian 116024, China. Contact e-mail: [email protected].
Journal of Materials Engineering and Performance
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