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<p>Ti–6Al–4&#xa0;V titanium alloy is widely used in high-performance engineering, biomedical and aerospace applications due to its high specific strength, high corrosion resistance. However, the high oxygen affinity of Ti–6Al–4&#xa0;V at high temperatures makes welding difficult, the welds can embrittle, residual stresses can be created, and brittle martensitic microstructures can form in the fusion zone. For industrial applications, a 3.15&#xa0;mm plate thickness is widely used for light structural and aerospace parts, this thickness provides complete laser penetration under selected weld conditions. An experimental study was performed on 3.15&#xa0;mm thick Ti–6Al–4&#xa0;V butt joints by applying a high-power disk laser welding system in the present study. Sixteen experimental trials were designed by using Taguchi Design of Experiments (DOE) approach and optimal welding parameters were determined to obtain defect-free weld joints. For preventing the contamination of the atmosphere, high purity argon shielding gas was provided at the top and root of the weld. The optimized weld joint was then subjected to PWHT at 750℃ and 910℃ to investigate the effect of the heat treatment on the microstructural evolution and mechanical properties of the weld. The mechanical properties were characterized by tensile testing and hardness measurement, whereas the microstructural changes were investigated using optical microscopy, SEM and EDS techniques. It was concluded from the results that the as-welded martensitic α′ microstructure was significantly altered by the PWHT, resulting in phase decomposition and microstructural refinement, which in turn caused a reduction in stress and an increase in ductility. Treatment at 750&#xa0;°C led to a desirable combination of strength and ductility, while treatment at 910&#xa0;°C resulted in more transformation to the α + β structure and an accompanying decrease in hardness and residual stress. PWHT resulted in more uniform hardness distribution over the weld zone and tensile behaviour was more indicative of better joint integrity than was the as-welded state. The study presents a systematic procedure to optimize laser welding parameters and PWHT conditions for Ti–6Al–4&#xa0;V alloy, giving useful insights to the correlation between post-weld thermal treatment, microstructural evolution and performance of the weld joint.</p>

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Effect of heat treatment on micro-structural characteristics and mechanical properties of optimized laser-welded Ti-6Al-4 V using disk type continuous laser welding

  • 期刊论文

  • 发表日期：

    2026年7月17日

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  • Chandragiri Reddy Prasad,
  • Nandure Narayan Rao

摘要

Ti–6Al–4 V titanium alloy is widely used in high-performance engineering, biomedical and aerospace applications due to its high specific strength, high corrosion resistance. However, the high oxygen affinity of Ti–6Al–4 V at high temperatures makes welding difficult, the welds can embrittle, residual stresses can be created, and brittle martensitic microstructures can form in the fusion zone. For industrial applications, a 3.15 mm plate thickness is widely used for light structural and aerospace parts, this thickness provides complete laser penetration under selected weld conditions. An experimental study was performed on 3.15 mm thick Ti–6Al–4 V butt joints by applying a high-power disk laser welding system in the present study. Sixteen experimental trials were designed by using Taguchi Design of Experiments (DOE) approach and optimal welding parameters were determined to obtain defect-free weld joints. For preventing the contamination of the atmosphere, high purity argon shielding gas was provided at the top and root of the weld. The optimized weld joint was then subjected to PWHT at 750℃ and 910℃ to investigate the effect of the heat treatment on the microstructural evolution and mechanical properties of the weld. The mechanical properties were characterized by tensile testing and hardness measurement, whereas the microstructural changes were investigated using optical microscopy, SEM and EDS techniques. It was concluded from the results that the as-welded martensitic α′ microstructure was significantly altered by the PWHT, resulting in phase decomposition and microstructural refinement, which in turn caused a reduction in stress and an increase in ductility. Treatment at 750 °C led to a desirable combination of strength and ductility, while treatment at 910 °C resulted in more transformation to the α + β structure and an accompanying decrease in hardness and residual stress. PWHT resulted in more uniform hardness distribution over the weld zone and tensile behaviour was more indicative of better joint integrity than was the as-welded state. The study presents a systematic procedure to optimize laser welding parameters and PWHT conditions for Ti–6Al–4 V alloy, giving useful insights to the correlation between post-weld thermal treatment, microstructural evolution and performance of the weld joint.