Fig. 1. Schematic of lap welding for 6061/5182 aluminum alloys.

린 첸 가오 양 미시 옹 장 춘밍 왕
Lin Chen , Gaoyang Mi , Xiong Zhang , Chunming Wang *
중국 우한시 화중과학기술대학 재료공학부, 430074

Effects of sinusoidal oscillating laser beam on weld formation, melt flow and grain structure during aluminum alloys lap welding

Abstract

A numerical model of 1.5 mm 6061/5182 aluminum alloys thin sheets lap joints under laser sinusoidal oscillation (sine) welding and laser welding (SLW) weld was developed to simulate temperature distribution and melt flow. Unlike the common energy distribution of SLW, the sinusoidal oscillation of laser beam greatly homogenized the energy distribution and reduced the energy peak. The energy peaks were located at both sides of the sine weld, resulting in the tooth-shaped sectional formation. This paper illustrated the effect of the temperature gradient (G) and solidification rate (R) on the solidification microstructure by simulation. Results indicated that the center of the sine weld had a wider area with low G/R, promoting the formation of a wider equiaxed grain zone, and the columnar grains were slenderer because of greater GR. The porosity-free and non-penetration welds were obtained by the laser sinusoidal oscillation. The reasons were that the molten pool volume was enlarged, the volume proportion of keyhole was reduced and the turbulence in the molten pool was gentled, which was observed by the high-speed imaging and simulation results of melt flow. The tensile test of both welds showed a tensile fracture form along the fusion line, and the tensile strength of sine weld was significantly better than that of the SLW weld. This was because that the wider equiaxed grain area reduced the tendency of cracks and the finer grain size close to the fracture location. Defect-free and excellent welds are of great significance to the new energy vehicles industry.

온도 분포 및 용융 흐름을 시뮬레이션하기 위해 레이저 사인파 진동 (사인) 용접 및 레이저 용접 (SLW) 용접에서 1.5mm 6061/5182 알루미늄 합금 박판 랩 조인트 의 수치 모델이 개발되었습니다. SLW의 일반적인 에너지 분포와 달리 레이저 빔의 사인파 진동은 에너지 분포를 크게 균질화하고 에너지 피크를 줄였습니다. 에너지 피크는 사인 용접의 양쪽에 위치하여 톱니 모양의 단면이 형성되었습니다. 이 논문은 온도 구배(G)와 응고 속도 의 영향을 설명했습니다.(R) 시뮬레이션에 의한 응고 미세 구조. 결과는 사인 용접의 중심이 낮은 G/R로 더 넓은 영역을 가짐으로써 더 넓은 등축 결정립 영역의 형성을 촉진하고 더 큰 GR로 인해 주상 결정립 이 더 가늘다는 것을 나타냅니다. 다공성 및 비관통 용접은 레이저 사인파 진동에 의해 얻어졌습니다. 그 이유는 용융 풀의 부피가 확대되고 열쇠 구멍의 부피 비율이 감소하며 용융 풀의 난류가 완만해졌기 때문이며, 이는 용융 흐름의 고속 이미징 및 시뮬레이션 결과에서 관찰되었습니다. 두 용접부 의 인장시험 은 융착선을 따라 인장파괴형태를인장강도사인 용접의 경우 SLW 용접보다 훨씬 우수했습니다. 이는 등축 결정립 영역이 넓을수록 균열 경향이 감소하고 파단 위치에 근접한 입자 크기가 미세 하기 때문입니다. 결함이 없고 우수한 용접은 신에너지 자동차 산업에 매우 중요합니다.

Fig. 1. Schematic of lap welding for 6061/5182 aluminum alloys.
Fig. 1. Schematic of lap welding for 6061/5182 aluminum alloys.
Fig. 2. Finite element mesh.
Fig. 2. Finite element mesh.
Fig. 3. Weld morphologies of cross-section and upper surface for the two welds: (a) sine pattern weld; (b) SLW weld.
Fig. 3. Weld morphologies of cross-section and upper surface for the two welds: (a) sine pattern weld; (b) SLW weld.
Fig. 4. Calculation of laser energy distribution: (a)-(c) sine pattern weld; (d)-(f) SLW weld.
Fig. 4. Calculation of laser energy distribution: (a)-(c) sine pattern weld; (d)-(f) SLW weld.
Fig. 5. The partially melted region of zone A.
Fig. 5. The partially melted region of zone A.
Fig. 6. The simulated profiles of melted region for the two welds: (a) SLW weld; (b) sine pattern weld.
Fig. 6. The simulated profiles of melted region for the two welds: (a) SLW weld; (b) sine pattern weld.
Fig. 7. The temperature field simulation results of cross section for sine pattern weld.
Fig. 7. The temperature field simulation results of cross section for sine pattern weld.
Fig. 8. Dynamic behavior of the molten pool at the same time interval of 0.004 s within one oscillating period: (a) SLW weld; (b) sine pattern weld.
Fig. 8. Dynamic behavior of the molten pool at the same time interval of 0.004 s within one oscillating period: (a) SLW weld; (b) sine pattern weld.
Fig. 9. The temperature field and flow field of the molten pool for the SLW weld: (a)~(f) t = 80 ms~100 ms.
Fig. 9. The temperature field and flow field of the molten pool for the SLW weld: (a)~(f) t = 80 ms~100 ms.
Fig. 10. The temperature field and flow field of the molten pool for the sine pattern weld: (a)~(f) t = 151 ms~171 ms.
Fig. 10. The temperature field and flow field of the molten pool for the sine pattern weld: (a)~(f) t = 151 ms~171 ms.
Fig. 11. The evolution of the molten pool volume and keyhole depth within one period.
Fig. 11. The evolution of the molten pool volume and keyhole depth within one period.
Fig. 12. The X-ray inspection results for the two welds: (a) SLW weld, (b) sine pattern weld.
Fig. 12. The X-ray inspection results for the two welds: (a) SLW weld, (b) sine pattern weld.
Fig. 13. Comparison of the solidification parameters for sine and SLW patterns: (a) the temperature field simulated results of the molten pool upper surfaces; (b) temperature gradient G and solidification rate R along the molten pool boundary isotherm from weld centerline to the fusion boundary; (c) G/R; (d) GR.
Fig. 13. Comparison of the solidification parameters for sine and SLW patterns: (a) the temperature field simulated results of the molten pool upper surfaces; (b) temperature gradient G and solidification rate R along the molten pool boundary isotherm from weld centerline to the fusion boundary; (c) G/R; (d) GR.
Fig. 14. The EBSD results of equiaxed grain zone in the weld center of: (a) sine pattern weld; (b) SLW weld; (c) grain size.
Fig. 14. The EBSD results of equiaxed grain zone in the weld center of: (a) sine pattern weld; (b) SLW weld; (c) grain size.
Fig. 15. (a) EBSD results of horizontal sections of SLW weld and sine pattern weld; (b) The columnar crystal widths of SLW weld and sine pattern weld.
Fig. 15. (a) EBSD results of horizontal sections of SLW weld and sine pattern weld; (b) The columnar crystal widths of SLW weld and sine pattern weld.
Fig. 16. (a) The tensile test results of the two welds; (b) Fracture location of SLW weld; (b) Fracture location of sine pattern weld.
Fig. 16. (a) The tensile test results of the two welds; (b) Fracture location of SLW weld; (b) Fracture location of sine pattern weld.

Keywords

Laser welding, Sinusoidal oscillating, Energy distribution, Numerical simulation, Molten pool flow, Grain structure

References

Chen, X., 2014. Study on laser-MAG Hybrid Weaving Welding Charateristics. Master
thesis. Harbin Institute of Technology, China.
Chen, G., Wang, B., Mao, S., Zhong, P., He, J., 2019. Research on the “∞”-shaped laser
scanning welding process for aluminum alloy. Opt. Laser Technol. 115, 32–41.
Cho, W.-I., Na, S.-J., Cho, M.-H., Lee, J.-S., 2010. Numerical study of alloying element
distribution in CO2 laser–GMA hybrid welding. Comput. Mater. Sci. 49, 792–800.
Cho, W.-I., Na, S.-J., Thomy, C., Vollertsen, F., 2012. Numerical simulation of molten
pool dynamics in high power disk laser welding. J. Mater. Process. Technol. 212,
262–275.
Das, A., Butterworth, I., Masters, I., Williams, D., 2018. Microstructure and mechanical
properties of gap-bridged remote laser welded (RLW) automotive grade AA 5182
joints. Mater. Charact. 145, 697–712.
Fetzer, F., Sommer, M., Weber, R., Weberpals, J.-P., Graf, T., 2018. Reduction of pores by
means of laser beam oscillation during remote welding of AlMgSi. Opt. Lasers Eng.
108, 68–77.
Geng, S., Jiang, P., Shao, X., Guo, L., Gao, X., 2020. Heat transfer and fluid flow and their
effects on the solidification microstructure in full-penetration laser welding of
aluminum sheet. J. Mater. Sci. Technol. 46, 50–63.
Hagenlocher, C., Sommer, M., Fetzer, F., Weber, R., Graf, T., 2018a. Optimization of the
solidification conditions by means of beam oscillation during laser beam welding of
aluminum. Mater. Des. 160, 1178–1185.
Hagenlocher, C., Weller, D., Weber, R., Graf, T., 2018b. Reduction of the hot cracking
susceptibility of laser beam welds in AlMgSi alloys by increasing the number of grain
boundaries. Sci. Technol. Weld. Join. 24, 313–319.
Hagenlocher, C., Fetzer, F., Weller, D., Weber, R., Graf, T., 2019. Explicit analytical
expressions for the influence of welding parameters on the grain structure of laser
beam welds in aluminium alloys. Mater. Des. 174, 107791.
Han, X., Tang, X., Wang, T., Shao, C., Lu, F., Cui, H., 2018. Role of ambient pressure in
keyhole dynamics based on beam transmission path method for laser welding on Al
alloy. Int. J. Adv. Manuf. Technol. 99, 1639–1651.
Hao, K., Li, G., Gao, M., Zeng, X., 2015. Weld formation mechanism of fiber laser
oscillating welding of austenitic stainless steel. J. Mater. Process. Technol. 225,
77–83.
Hirt, C.W., Nichols, B.D., 1981. Volume of fluid (VOF) method for the dynamics of free
boundaries. J. Comput. Phys. 39, 201–225.
Jiang, Z., Chen, X., Li, H., Lei, Z., Chen, Y., Wu, S., Wang, Y., 2020. Grain refinement and
laser energy distribution during laser oscillating welding of Invar alloy. Mater. Des.
186, 108195.
Kaplan, A., 1994. A model of deep penetration laser welding based on calculation of the
keyhole profile. J. Phys. D Appl. Phys. 27, 1805–1814.
Kou, S., 2002. Welding Metallurgy, 2nd ed. Wiley-Interscience, New Jersey, USA.
Kuryntsev, S.V., Gilmutdinov, A.K., 2015. The effect of laser beam wobbling mode in
welding process for structural steels. Int. J. Adv. Manuf. Technol. 81, 1683–1691.
Li, P., Nie, F., Dong, H., Li, S., Yang, G., Zhang, H., 2018. Pulse MIG welding of 6061-T6/
A356-T6 aluminum alloy dissimilar T-joint. J. Mater. Eng. Perform. 27, 4760–4769.
Liu, T., Mu, Z., Hu, R., Pang, S., 2019. Sinusoidal oscillating laser welding of 7075
aluminum alloy: hydrodynamics, porosity formation and optimization. Int. J. Heat
Mass Transf. 140, 346–358.
Seto, N., Katayama, S., Matsunawa, A., 2000. High-speed simultaneous observation of
plasma and keyhole behavior during high power CO2 laser welding: effect of
shielding gas on porosity formation. J. Laser Appl. 12, 245–250.
Tang, Z., Vollertsen, F., 2014. Influence of grain refinement on hot cracking in laser
welding of aluminum. Weld. World 58, 355–366.
Wang, L., Gao, M., Zhang, C., Zeng, X., 2016. Effect of beam oscillating pattern on weld
characterization of laser welding of AA6061-T6 aluminum alloy. Mater. Des. 108,
707–717.
Wang, L., Gao, M., Zeng, X., 2018. Experiment and prediction of weld morphology for
laser oscillating welding of AA6061 aluminium alloy. Sci. Technol. Weld. Join. 24,
334–341.
Yamazaki, Y., Abe, Y., Hioki, Y., Nakatani, M., Kitagawa, A., Nakata, K., 2016.
Fundamental study of narrow-gap welding with oscillation laser beam. Weld. Int. 30,
699–707.
Yuan, Z., Tu, Y., Yuan, T., Zhang, Y., Huang, Y., 2021. Size effects on mechanical
properties of pure industrial aluminum sheet for micro/meso scale plastic
deformation: experiment and modeling. J. Alloys. Compd. 859, 157752.
Zou, J., 2016. Characteristics of laser scanning welding process for 5A06 aluminum alloy
thick plate with narrow gap. Materials Processing Engineering. Harbin Welding
Institute, China. Master thesis.

PDF VIEW