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Evaluation of Mechanical Properties of AZ61 Magnesium Alloy Joints at various Welding Speeds

용접 속도에 따른 AZ61 마그네슘 합금 마찰교반용접부 기계적 특성 평가

  • Sun, Seung-Ju (Advanced Materials Research Team, Korea Railroad Research Institute) ;
  • Kim, Jung-Seok (Advanced Materials Research Team, Korea Railroad Research Institute) ;
  • Lee, Woo-Geun (Advanced Materials Research Team, Korea Railroad Research Institute) ;
  • Lim, Jae-Yong (School of Mechanical Engineering, Daegu University)
  • Received : 2017.04.14
  • Accepted : 2017.05.12
  • Published : 2017.05.31

Abstract

In this study, the heat input conditions suitable for the AZ61 magnesium alloy were derived by controlling the welding speed at a constant rotational speed. In addition, from an economic point of view, industry demands higher welding speeds. Therefore,the effects of the welding speed were studied. The rotational speed applied was 800rpm, and the welding speed was varied from 100 to 500mm/min to evaluate the behavior of the welded regions. Tensile and hardness tests were conducted to examine the mechanical properties. Optical microscopy was used to observe the microstructure and soundness of the welded regions. Defects were observed at the welded region when the welding speed was more than400mm/min. As the welding speed increased, the grain size of the stir zone decreased and the hardness tended to increase proportionally. When the rotational speed was 800 rpm and the welding speed was 200mm/min and 300mm/min, there wereno defects in the welded region and excellent mechanical properties were recorded. In addition, the joint efficiencies were 100.5% and 101.2%, respectively, and the ultimate tensile strength was similar to that of the base metal. Fracture of the tensile specimen occurred between the advancing side and stir zone, and the fracture location coincided with the region where the hardness decreased temporarily.

Keywords

Friction Stir Welding;Hardness;Magnesium Alloys;Microstructure;Tensile test

Acknowledgement

Supported by : 한국철도기술연구원

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