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<p>This study successfully obtained 7A85 high-ribbed panels friction stir-welded (FSW) joints through proportional parameter changed (<i>ω</i>: 400–1200&#xa0;rpm; <i>v</i>: 100–300&#xa0;mm/min) and further optimized the mechanical properties of the FSW joints through artificial aging. The effects of welding process parameters and artificial aging on the microstructure and mechanical properties of the welded joint were investigated using OM, SEM, EBSD, TEM, tensile testing, and hardness testing. The results showed that the joint consists of the weld nucleus zone (NZ), thermomechanical influence zone (TMAZ), heat-affected zone (HAZ) and base metal (BM). Among these, the NZ undergoes significant dynamic recrystallization under thermomechanical coupling, with the degree of recrystallization increasing gradually from top to bottom along the thickness direction. When the welding pitch remains constant, increasing the welding speed reduces heat input and effectively suppresses the coarsening of precipitates in the HAZ. After aging, the GP zone in the NZ transforms into the strengthening η′ phase, while the coarsening in the HAZ is further suppressed. Mechanical tests indicate that increasing the parameters from <i>ω</i> = 400&#xa0;rpm/<i>v</i> = 100&#xa0;mm/min to <i>ω</i> = 1200&#xa0;rpm/<i>v</i> = 300&#xa0;mm/min can enhance tensile strength from 432 to 463&#xa0;MPa, yield strength from 332 to 377&#xa0;MPa, while reducing elongation from 6.2% to 5.2%. Increasing the proportional parameters enhances strength with limited loss of elongation, but expands the weakened zone of the TMAZ/HAZ. Therefore, welding process parameters of <i>ω</i> = 800&#xa0;rpm and <i>v</i> = 200&#xa0;mm/min yield excellent microstructural characteristics and optimal performance.</p>

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The effects of process parameters and heat treatment on microstructure evolution and mechanical properties of 7A85 aluminum alloy friction stir welded joints

  • 期刊论文

  • 发表日期：

    2025年9月10日

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  • Yu Juan,
  • Congcong Zhu,
  • Fan Zhenzhong,
  • Wu Zhigang,
  • Tong Gaungze,
  • Gao Wenli

摘要

This study successfully obtained 7A85 high-ribbed panels friction stir-welded (FSW) joints through proportional parameter changed (ω: 400–1200 rpm; v: 100–300 mm/min) and further optimized the mechanical properties of the FSW joints through artificial aging. The effects of welding process parameters and artificial aging on the microstructure and mechanical properties of the welded joint were investigated using OM, SEM, EBSD, TEM, tensile testing, and hardness testing. The results showed that the joint consists of the weld nucleus zone (NZ), thermomechanical influence zone (TMAZ), heat-affected zone (HAZ) and base metal (BM). Among these, the NZ undergoes significant dynamic recrystallization under thermomechanical coupling, with the degree of recrystallization increasing gradually from top to bottom along the thickness direction. When the welding pitch remains constant, increasing the welding speed reduces heat input and effectively suppresses the coarsening of precipitates in the HAZ. After aging, the GP zone in the NZ transforms into the strengthening η′ phase, while the coarsening in the HAZ is further suppressed. Mechanical tests indicate that increasing the parameters from ω = 400 rpm/v = 100 mm/min to ω = 1200 rpm/v = 300 mm/min can enhance tensile strength from 432 to 463 MPa, yield strength from 332 to 377 MPa, while reducing elongation from 6.2% to 5.2%. Increasing the proportional parameters enhances strength with limited loss of elongation, but expands the weakened zone of the TMAZ/HAZ. Therefore, welding process parameters of ω = 800 rpm and v = 200 mm/min yield excellent microstructural characteristics and optimal performance.