Journal of the Korea Academia-Industrial cooperation Society (한국산학기술학회논문지)

The Korea Academia-Industrial cooperation Society (한국산학기술학회)
권호 표지
DOI QR코드

DOI QR Code

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
Download PDF
⟨ Previous Next ⟩

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.

본 연구에서는 일정한 회전 속도에서 용접 속도를 제어하여 AZ61 마그네슘 합금에 적합한 입열량 조건을 도출하였다. 또한 산업적 측면에서는 더 빠른 용접 속도가 요구되기 때문에 용접 속도에 따른 효과를 연구하였다. 회전 속도 변수는 800rpm으로 일정하게 적용하였고, 용접 속도는 100 - 500mm/min 으로 변화시켜 용접부의 거동을 관찰 및 평가하였다. 기계적 물성 평가를 위하여 인장 및 경도 시험을 수행하였으며, 미세구조 관찰과 용접부의 건정성을 판단하기 위하여 광학현미경을 사용하였다. 용접 속도가 400mm/min 이상 적용되었을 때 용접부 내부에서 결함이 관찰되었다. 용접 속도가 증가할수록 교반부의 결정립 크기는 작아졌으며, 경도 또한 비례 증가하는 경향을 보였다. 회전속도 800rpm, 용접 속도 200mm/min과 300mm/min 일 때, 용접부 내 외부 적으로 결함이 없었으며, 우수한 기계적 물성이 기록되었다. 이때, 접합 효율은 각각 100.5%, 101.2%이었고, 최대인장강도가 모재의 강도와 유사하였다. 인장 시편의 파괴는 시편의 전진측과 교반부 사이에서 발생하였으며, 이는 횡단면부 경도 분포에서 경도가 일시적으로 감소하는 위치와 일치하였다.

Keywords

References

  1. D. H. Jang, 'Process Development for Automotive Hybrid Hood using Magnesium Alloy AZ31B Sheet', Transactions of Materials Processing, vol. 20, no. 2, pp. 160-166, 2011. DOI: https://doi.org/10.5228/KSTP.2011.20.2.160
  2. H. B. Chen, K. Yan, T. Lin, S. B. Chen, C. Y. Jiang, Y. Zhao, "The investigation of typical welding defects for 5456 aluminum alloy friction stir welds", Materials Science and Engineering: A, vol. 433, no. 1, pp. 64-69, 2006. DOI: https://doi.org/10.1016/j.msea.2006.06.056
  3. R. S. Mishra, Z. Y. Ma, "Friction stir welding and processing", Materials Science and Engineering: R: Reports, vol. 50, no. 1, pp. 1-78, 2005. DOI: https://doi.org/10.1016/j.mser.2005.07.001
  4. O. Frigaard, O. Grong, B. Bjorneklett, OT. Midling, In Proceedings of the 1st international symposium on friction stir welding, Thousand Oaks, CA, USA; 14-16 June, 1999.
  5. M. S. Moghaddam,, R. Parvizi, M. Haddad- Sabzevar, A. Davoodi, "Microstructural and mechanical properties of friction stir welded Cu-30Zn brass alloy at various feed speeds: Influence of stir bands", Materials & Design, vol. 32, no. 5, pp. 2749-2755, 2011. DOI: https://doi.org/10.1016/j.matdes.2011.01.015
  6. Z. W. Chen, T. Pasang, Y. Qi, "Shear flow and formation of Nugget zone during friction stir welding of aluminium alloy 5083-O", Materials Science and Engineering: A, vol. 474, no. 1, pp. 312-316, 2008. DOI: https://doi.org/10.1016/j.msea.2007.05.074
  7. N. Afrin, D. L. Chen, X. Cao, M. Jahazi, "Microstructure and tensile properties of friction stir welded AZ31B magnesium alloy", Materials Science and Engineering: A, 472(1), 179-186, 2008. DOI: https://doi.org/10.1016/j.msea.2007.03.018
  8. Y. G. Kim, H. Fujii, T. Tsumura, T. Komazaki, K. Nakata, "Three defect types in friction stir welding of aluminum die casting alloy", Materials Science and Engineering: A, vol. 415, no. 1, pp. 250-254, 2006. DOI: https://doi.org/10.1016/j.msea.2005.09.072
  9. Y. B. Tan, X. M. Wang, M. Ma, J. X. Zhang, W. C. Liu, R. D. Fu S. Xiang, "A study on microstructure and mechanical properties of AA 3003 aluminum alloy joints by underwater friction stir welding", Materials Characterization, vol. 127, pp. 41-52, 2017. DOI: https://doi.org/10.1016/j.matchar.2017.01.039
  10. G. M. Xie, Z. Y. Ma, L. Geng, "Development of a fine-grained microstructure and the properties of a nugget zone in friction stir welded pure copper", Scripta Materialia, vol. 57, no. 2, pp. 73-76, 2007. DOI: https://doi.org/10.1016/j.scriptamat.2007.03.048
  11. G. M. Xie, Z. Y. Ma, L. Geng, "Development of a fine-grained microstructure and the properties of a nugget zone in friction stir welded pure copper", Scripta Materialia, vol. 57, no. 2, pp. 73-76, 2007. DOI: https://doi.org/10.1016/j.scriptamat.2007.03.048
  12. T. Hirata, T. Oguri, H. Hagino, T. Tanaka, S. W. Chung, Y. Takigawa, K. Higashi, "Influence of friction stir welding parameters on grain size and formability in 5083 aluminum alloy," Materials Science and Engineering: A, vol. 456, no. 1, pp.344-349, 2007. DOI: https://doi.org/10.1016/j.msea.2006.12.079
  13. S. H. C. Park, Y. S. Sato, H. Kokawa, "Microstructural evolution and its effect on Hall-Petch relationship in friction stir welding of thixomolded Mg alloy AZ91D," Journal of materials science, vol. 38, no. 21, pp. 4379-4383, 2003. DOI: https://doi.org/10.1023/A:1026351619636
  14. S. H. C. Park, Y. S. Sato, H. Kokawa, "Effect of micro-texture on fracture location in friction stir weld of Mg alloy AZ61 during tensile test", Scripta Materialia, vol. 49, no. 2, pp. 161-166, 2003. DOI: https://doi.org/10.1016/S1359-6462(03)00210-0
  15. E. O. Hall, "The deformation and ageing of mild steel: III discussion of results", Proceedings of the Physical Society Section B, vol. 64, no. 9, pp. 747, 1951. DOI: https://doi.org/10.1088/0370-1301/64/9/303
  16. N. J. Petch, "The cleavage strength of polycrystals", The Journal of the Iron and Steel Institute, vol. 174, pp. 25-28, 1953.
  17. H. J. Liu, H. Fujii, M. Maeda, K. Nogi, "Tensile properties and fracture locations of friction-stir- welded joints of 2017-T351 aluminum alloy", Journal of Materials Processing Technology, vol. 142, no. 3, pp. 692-696, 2003. DOI: https://doi.org/10.1016/S0924-0136(03)00806-9
  18. J. Yang, D. Wang, B. L. Xiao, D. R. Ni, Z. Y. Ma, "Effects of rotation rates on microstructure, mechanical properties, and fracture behavior of friction stir-welded (FSW) AZ31 magnesium alloy", Metallurgical and Materials Transactions A, vol. 44, no. 1, pp. 517-530, 2013. DOI: https://doi.org/10.1007/s11661-012-1373-4
  19. W. Woo, H. Choo, D. W. Brown, P. K. Liaw, Z. Feng, "Texture variation and its influence on the tensile behavior of a friction-stir processed magnesium alloy", Scripta materialia, vol. 54, no. 11, pp. 1859-1864, 2006. DOI: https://doi.org/10.1016/j.scriptamat.2006.02.019