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<p>Vacuum laser beam welding (VLBW) of Ti6321-thick plates plays a pivotal role in the development of large-scale marine equipment. However, the embrittlement of the heat-affected zone (HAZ) in Ti6321 welded joints severely damages the operational performance. This study systematically investigates the effect of post-weld heat treatment (PWHT) on the microstructure and toughness of the HAZ in VLBW-welded joints of Ti6321-thick plates. The results indicate that after the 850 ℃/1&#xa0;h/FC treatment, the α/β-stabilizing elements (Al, Mo, Nb) in α’ diffuse and segregate sufficiently. Specifically, Al accumulated at the α’ boundaries to form lamellar α, while Mo and Nb segregated around the α’ to form lamellar β. This microstructural evolution (α’ to lamellar α/β) enhanced the HAZ toughness by 39%, which was attributed to two key aspects from the perspective of crystallographic characteristics: the driving force for crack initiation was reduced by the reduction of lattice distortion and the improvement of deformation compatibility; the resistance to crack propagation was improved by the increase in proportion of high-angle grain boundaries (HAGBs) and the decrease in texture intensity. This work provides a potential approach to improve the quality of Ti6321 welded joints.</p>

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Effects of post-weld heat treatment on the HAZ of VLBW-fabricated Ti6321 joints: elemental redistribution, microstructural evolution, and mechanical property

  • 期刊论文

  • 发表日期：

    2026年5月12日

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  • Peng Yu,
  • Fangjie Cheng,
  • Shuaifeng Zhang,
  • Jiaming Chen,
  • Zhendan Zheng,
  • Shuai Yan,
  • Pengfei Tian,
  • Shaojie Wu

摘要

Vacuum laser beam welding (VLBW) of Ti6321-thick plates plays a pivotal role in the development of large-scale marine equipment. However, the embrittlement of the heat-affected zone (HAZ) in Ti6321 welded joints severely damages the operational performance. This study systematically investigates the effect of post-weld heat treatment (PWHT) on the microstructure and toughness of the HAZ in VLBW-welded joints of Ti6321-thick plates. The results indicate that after the 850 ℃/1 h/FC treatment, the α/β-stabilizing elements (Al, Mo, Nb) in α’ diffuse and segregate sufficiently. Specifically, Al accumulated at the α’ boundaries to form lamellar α, while Mo and Nb segregated around the α’ to form lamellar β. This microstructural evolution (α’ to lamellar α/β) enhanced the HAZ toughness by 39%, which was attributed to two key aspects from the perspective of crystallographic characteristics: the driving force for crack initiation was reduced by the reduction of lattice distortion and the improvement of deformation compatibility; the resistance to crack propagation was improved by the increase in proportion of high-angle grain boundaries (HAGBs) and the decrease in texture intensity. This work provides a potential approach to improve the quality of Ti6321 welded joints.