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<p>This study systematically investigated the fatigue property evolution of 2024-T4 aluminum alloy welds subjected to ultrasonic impact treatment (UIT) under varying pre-service cycles. Through multi-scale analysis integrating microstructural characterization, microhardness testing, residual stress measurement via SINTMTS3000 hole-drilling method, and SEM fractography, the dynamic influence mechanisms of pre-service duration on UIT effectiveness were elucidated. Results demonstrate that UIT produces nanoscale grain refinement and forms a strengthened surface layer (45-60&#xa0;μm depth) containing − 841 MPa compressive residual stress field. The average microhardness increases from 110 HV to 132 HV in heat-affected zones, and from 123 HV to 150 HV in weld nugget zones, delaying fatigue crack initiation/propagation and enhancing fatigue life by 167% compared to as-welded specimens. However, when subsequent UIT is applied after 25% and 50% service life, the fatigue life improvement decreases to 141% and 58%, respectively. At 75% pre-service duration, significant gradient attenuation of compressive stress fields (− 500 MPa reduction) occurs with increased crack depth, rendering UIT’s effectiveness comparable to untreated welds. This phenomenon is primarily attributed to cyclic loading-induced effects and residual stress field reconfiguration, providing a theoretical basis for evaluating the time-dependent effectiveness of strengthening processes in engineering practice.</p>

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Effect of Ultrasonic Impact Treatment on the Fatigue Properties of Pre-service 2024-T4 Aluminum Alloy Welded Joints

  • 期刊论文

  • 发表日期：

    2025年11月14日

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  • Jiahui Cong,
  • Zhuo Liu,
  • Song Zhou,
  • Xuyang Zhu,
  • Shoulong Gao

摘要

This study systematically investigated the fatigue property evolution of 2024-T4 aluminum alloy welds subjected to ultrasonic impact treatment (UIT) under varying pre-service cycles. Through multi-scale analysis integrating microstructural characterization, microhardness testing, residual stress measurement via SINTMTS3000 hole-drilling method, and SEM fractography, the dynamic influence mechanisms of pre-service duration on UIT effectiveness were elucidated. Results demonstrate that UIT produces nanoscale grain refinement and forms a strengthened surface layer (45-60 μm depth) containing − 841 MPa compressive residual stress field. The average microhardness increases from 110 HV to 132 HV in heat-affected zones, and from 123 HV to 150 HV in weld nugget zones, delaying fatigue crack initiation/propagation and enhancing fatigue life by 167% compared to as-welded specimens. However, when subsequent UIT is applied after 25% and 50% service life, the fatigue life improvement decreases to 141% and 58%, respectively. At 75% pre-service duration, significant gradient attenuation of compressive stress fields (− 500 MPa reduction) occurs with increased crack depth, rendering UIT’s effectiveness comparable to untreated welds. This phenomenon is primarily attributed to cyclic loading-induced effects and residual stress field reconfiguration, providing a theoretical basis for evaluating the time-dependent effectiveness of strengthening processes in engineering practice.