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<p>In this study, the effects of Laser Shock Peening (LSP) on the Residual Stress, Stress Corrosion Cracking (SCC) behaviour and surface topography of AA2219 T87 Friction Stir Weld (FSW) joints were investigated. Laser shock peening was performed on crown and root sides of the weld. The longitudinal through-thickness residual stress was evaluated using contour method for both the unpeened (as-welded) and peened FSW plates. In as-welded condition, a non-uniform longitudinal tensile residual stress was present near the weld center throughout the thickness of the specimen. The peak tensile residual stress was 41 pct of the yield strength of the base metal at the middle thickness of the weld. Laser shock peening (six layers) resulted in a reduction in the tensile residual stress throughout the thickness and across all regions of the weld. The peak tensile residual stress reduced to +65 MPa from +160 MPa (<i>i.e.</i>, 59 pct reduction) after six layers of laser shock peening. Transmission Electron Microscopic study revealed an increase in dislocation density and the formation of dislocation tangles due to the six layers of laser shock peening, which reduced the tensile residual stress. Stress corrosion cracking resistance was evaluated using slow strain rate test in air and NaCl environments. The ultimate tensile strength and elongation values are similar irrespective of the condition of the specimen (unpeened or peened) and environment (air or NaCl). The fractography of the failed specimens indicated the absence of intergranular corrosion. Good stress corrosion cracking resistance of laser shock peened specimens was confirmed by the SCC index (&gt; 0.94) and fractographic examination of the samples. The laser shock peening increased the surface roughness in all the regions and the increase was substantial in the Weld Nugget (WN) and Thermo Mechanically Affected Zone (TMAZ), which are the softest regions of the weld. Repeated layers of LSP led to a progressive increase in the surface roughness, similar to the microhardness survey results. The increase in the surface roughness did not offset the benefits of laser shock peening in terms of reducing the tensile residual stress and resistance to stress corrosion cracking. In this study, laser shock peening of AA2219 T87 FSW joint led to significant reduction in tensile residual stress throughout the thickness, which is useful for ensuring structural integrity and improving fracture margins of aerospace pressure vessels. This study also highlighted that the stress corrosion cracking behaviour of AA2219 T87 FSW is not compromised due to laser shock peening, which is one of the most important requirements for space launch vehicles.</p>

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Investigation on the Effect of Laser Shock Peening on Residual Stress, Stress Corrosion Cracking Behaviour and Surface Roughness of AA2219 Friction Stir Weld

  • 期刊论文

  • 发表日期：

    2026年2月25日

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  • M. P. Dhanasekaran,
  • M. Agilan,
  • S. Anoop,
  • K. N. Vidyananda,
  • R. Muthukumar,
  • D. Roy Mahapatra

摘要

In this study, the effects of Laser Shock Peening (LSP) on the Residual Stress, Stress Corrosion Cracking (SCC) behaviour and surface topography of AA2219 T87 Friction Stir Weld (FSW) joints were investigated. Laser shock peening was performed on crown and root sides of the weld. The longitudinal through-thickness residual stress was evaluated using contour method for both the unpeened (as-welded) and peened FSW plates. In as-welded condition, a non-uniform longitudinal tensile residual stress was present near the weld center throughout the thickness of the specimen. The peak tensile residual stress was 41 pct of the yield strength of the base metal at the middle thickness of the weld. Laser shock peening (six layers) resulted in a reduction in the tensile residual stress throughout the thickness and across all regions of the weld. The peak tensile residual stress reduced to +65 MPa from +160 MPa (i.e., 59 pct reduction) after six layers of laser shock peening. Transmission Electron Microscopic study revealed an increase in dislocation density and the formation of dislocation tangles due to the six layers of laser shock peening, which reduced the tensile residual stress. Stress corrosion cracking resistance was evaluated using slow strain rate test in air and NaCl environments. The ultimate tensile strength and elongation values are similar irrespective of the condition of the specimen (unpeened or peened) and environment (air or NaCl). The fractography of the failed specimens indicated the absence of intergranular corrosion. Good stress corrosion cracking resistance of laser shock peened specimens was confirmed by the SCC index (> 0.94) and fractographic examination of the samples. The laser shock peening increased the surface roughness in all the regions and the increase was substantial in the Weld Nugget (WN) and Thermo Mechanically Affected Zone (TMAZ), which are the softest regions of the weld. Repeated layers of LSP led to a progressive increase in the surface roughness, similar to the microhardness survey results. The increase in the surface roughness did not offset the benefits of laser shock peening in terms of reducing the tensile residual stress and resistance to stress corrosion cracking. In this study, laser shock peening of AA2219 T87 FSW joint led to significant reduction in tensile residual stress throughout the thickness, which is useful for ensuring structural integrity and improving fracture margins of aerospace pressure vessels. This study also highlighted that the stress corrosion cracking behaviour of AA2219 T87 FSW is not compromised due to laser shock peening, which is one of the most important requirements for space launch vehicles.