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<p>This paper systematically investigates the influence of surface pre-deformation on the microstructure evolution and mechanical properties of 7050 aluminum alloy using ultrasonic surface rolling processing (USRP) followed by aging treatment. The results indicate that USRP forms a grain gradient layer with a depth of 160 µm on the surface. After aging, the surface precipitates coarsen significantly, forming η phases. With increasing depth, the precipitate size decreases while density increases, and the precipitates in the sample core transform into finely dispersed η’ phases. This microstructural distribution results in lower surface microhardness (177 HV) compared to the core and unrolled specimens (205 HV), yet without a reduction in strength or ductility. This phenomenon occurs because the grain gradient structure generates a high density of geometrically necessary dislocations (GNDs) during loading, leading to hetero-deformation-induced (HDI) strengthening. Loading and unloading calculations reveal that the grain gradient structure in the USRP sample significantly enhances additional back stress, compensating for the strength loss caused by precipitate coarsening on the surface. Furthermore, the coarse η phase precipitated in the rolled layer due to pre-deformation reduces the electrochemical difference between the grain boundaries and the matrix, improving corrosion resistance. This dual-gradient structure in aluminum alloy is expected to achieve an optimal balance between mechanical strength and corrosion resistance.</p>

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Effect of Surface Pre-Deformation on Precipitation Behavior and Mechanical Properties of 7050 Aluminum Alloy

  • 期刊论文

  • 发表日期：

    2025年7月22日

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  • Liqian Wang,
  • Lei Zhou,
  • Zisheng Zhang,
  • Pingwei Xu,
  • Yingfei Guo,
  • Fei Zhao,
  • Ming Yang,
  • Longxiang Wang,
  • Yonghai Ren,
  • Wei Zhao,
  • Yu Liang

摘要

This paper systematically investigates the influence of surface pre-deformation on the microstructure evolution and mechanical properties of 7050 aluminum alloy using ultrasonic surface rolling processing (USRP) followed by aging treatment. The results indicate that USRP forms a grain gradient layer with a depth of 160 µm on the surface. After aging, the surface precipitates coarsen significantly, forming η phases. With increasing depth, the precipitate size decreases while density increases, and the precipitates in the sample core transform into finely dispersed η’ phases. This microstructural distribution results in lower surface microhardness (177 HV) compared to the core and unrolled specimens (205 HV), yet without a reduction in strength or ductility. This phenomenon occurs because the grain gradient structure generates a high density of geometrically necessary dislocations (GNDs) during loading, leading to hetero-deformation-induced (HDI) strengthening. Loading and unloading calculations reveal that the grain gradient structure in the USRP sample significantly enhances additional back stress, compensating for the strength loss caused by precipitate coarsening on the surface. Furthermore, the coarse η phase precipitated in the rolled layer due to pre-deformation reduces the electrochemical difference between the grain boundaries and the matrix, improving corrosion resistance. This dual-gradient structure in aluminum alloy is expected to achieve an optimal balance between mechanical strength and corrosion resistance.