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<p>Laser-welded 6061 aluminum alloy joints are often limited by high residual stresses, pronounced microstructural heterogeneity, and inferior mechanical properties, while the mechanisms by which post-weld laser heat treatment regulates stress evolution and joint performance remain insufficiently understood. In this study, a sequentially coupled thermo-mechanical model, validated by temperature and residual stress measurements, was developed to investigate the effects of laser heat treatment parameters on residual stress relaxation, microstructural evolution, and mechanical properties. The results indicate that post-weld laser heat treatment effectively relaxes the longitudinal residual stress, reducing the peak residual stress at the weld center from 226 to 41.4&#xa0;MPa, corresponding to a reduction of up to 81.7 pct. Meanwhile, the treatment promotes dendrite fragmentation and partial dissolution, accompanied by a transition from columnar to equiaxed grains near the fusion line. An optimal combination of residual stress reduction and mechanical performance was achieved at a laser power of 250 W, with a yield strength, ultimate tensile strength, and elongation of 140.3&#xa0;MPa, 239&#xa0;MPa, and 5.9 pct, respectively. Overall, the results demonstrate that a suitably controlled post-weld laser heat treatment strategy can achieve an effective balance between residual stress relaxation and strength–ductility enhancement, providing new insights into the underlying mechanisms governing the strength–ductility enhancement of laser-welded 6061 aluminum alloy joints.</p>

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Residual Stress Evolution, Microstructural Transformation, and Mechanical Performance of Aluminum Alloy Joints Subjected to Post-Weld Laser Heat Treatment: A Numerical–Experimental Study

  • 期刊论文

  • 发表日期：

    2026年7月21日

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  • Qunli Zhang,
  • Yetian Xu,
  • Zhijun Chen,
  • Yangfan Wang,
  • Gaolin Yang,
  • Szymon Tofil,
  • Jianhua Yao

摘要

Laser-welded 6061 aluminum alloy joints are often limited by high residual stresses, pronounced microstructural heterogeneity, and inferior mechanical properties, while the mechanisms by which post-weld laser heat treatment regulates stress evolution and joint performance remain insufficiently understood. In this study, a sequentially coupled thermo-mechanical model, validated by temperature and residual stress measurements, was developed to investigate the effects of laser heat treatment parameters on residual stress relaxation, microstructural evolution, and mechanical properties. The results indicate that post-weld laser heat treatment effectively relaxes the longitudinal residual stress, reducing the peak residual stress at the weld center from 226 to 41.4 MPa, corresponding to a reduction of up to 81.7 pct. Meanwhile, the treatment promotes dendrite fragmentation and partial dissolution, accompanied by a transition from columnar to equiaxed grains near the fusion line. An optimal combination of residual stress reduction and mechanical performance was achieved at a laser power of 250 W, with a yield strength, ultimate tensile strength, and elongation of 140.3 MPa, 239 MPa, and 5.9 pct, respectively. Overall, the results demonstrate that a suitably controlled post-weld laser heat treatment strategy can achieve an effective balance between residual stress relaxation and strength–ductility enhancement, providing new insights into the underlying mechanisms governing the strength–ductility enhancement of laser-welded 6061 aluminum alloy joints.