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<p>Narrow-gap laser-arc hybrid welding (NG-LAHW) of thick plate exhibits significant application prospects for manufacturing of large-scale structures in various fields. The microstructure and mechanical property uniformity of joints are the key factor for weld quality and structural reliability. In this study, the influences of microstructure inhomogeneity on mechanical properties of 16&#xa0;mm-thick titanium alloy joints fabricated by NG-LAHW were clarified. A progressive 72 pct reduction in columnar grain size and 74 pct decrease in equiaxed grain size from the cover layer to the back layer was observed, with finer <i>α'</i>-martensite and a higher density of grain boundaries in the back layer. Consequently, the back layer exhibited the highest hardness of 388.6 HV. The cover layer exhibited the lowest average impact energy of 11.6&#xa0;J with significant data fluctuations, while both the filled and back layers demonstrated comparable averages of 12.3&#xa0;J, equivalent to 93.9 pct of the impact energy of base metal. The reduction of welding heat input coupled with thermal treatment by subsequent welding pass promoted microstructural refinement and homogeneity, contributing to the enhancement of hardness and impact property of the back layer. These findings could provide a reference for the application of NG-LAHW technique for thick plate components manufacturing.</p>

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Inhomogeneous Microstructure and Mechanical Properties of Narrow-Gap Oscillating Laser-MIG Hybrid Welded 16 mm-Thick Titanium Alloy Joints

  • 期刊论文

  • 发表日期：

    2025年8月6日

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  • Chuang Cai,
  • Ping Tang,
  • Jie Yu,
  • Zilin Chen,
  • Zhenxin Li,
  • Fashuai Xiong,
  • Chendong Shao,
  • Fenggui Lu,
  • Hui Chen

摘要

Narrow-gap laser-arc hybrid welding (NG-LAHW) of thick plate exhibits significant application prospects for manufacturing of large-scale structures in various fields. The microstructure and mechanical property uniformity of joints are the key factor for weld quality and structural reliability. In this study, the influences of microstructure inhomogeneity on mechanical properties of 16 mm-thick titanium alloy joints fabricated by NG-LAHW were clarified. A progressive 72 pct reduction in columnar grain size and 74 pct decrease in equiaxed grain size from the cover layer to the back layer was observed, with finer α'-martensite and a higher density of grain boundaries in the back layer. Consequently, the back layer exhibited the highest hardness of 388.6 HV. The cover layer exhibited the lowest average impact energy of 11.6 J with significant data fluctuations, while both the filled and back layers demonstrated comparable averages of 12.3 J, equivalent to 93.9 pct of the impact energy of base metal. The reduction of welding heat input coupled with thermal treatment by subsequent welding pass promoted microstructural refinement and homogeneity, contributing to the enhancement of hardness and impact property of the back layer. These findings could provide a reference for the application of NG-LAHW technique for thick plate components manufacturing.