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<p>Dissimilar laser welding of AA7075 aluminum and Ti-6Al-4&#xa0;V titanium alloys is promising for lightweight structures, but the formation of brittle Ti/Al intermetallic compounds (IMCs) can degrade local mechanical integrity and creep resistance. This work evaluates whether introducing a copper (Cu) interlayer during laser beam welding can enhance the local nanomechanical response and room-temperature nanocreep behavior of AA7075/Ti-6Al-4&#xa0;V joints. Butt welds were produced using a 380-µm Cu foil, and depth-sensing nanoindentation was applied to map nanohardness, elastic modulus, and indentation creep across the AA7075 heat-affected zone (HAZ), fusion zone (FZ), mix zone, and the Cu/Ti-6Al-4&#xa0;V interface. Atomic force microscopy was used to characterize indentation-induced surface relief. The Cu interlayer increased nanohardness from 1.37 GPa in the AA7075 HAZ to 5.81 GPa at the Cu/Ti-6Al-4&#xa0;V interface and increased elastic modulus from 64.1 to 73.2 GPa. The maximum creep displacement (~ 176&#xa0;nm) occurred in the AA7075 HAZ with <i>n</i> ≈ 2.1, indicating grain-boundary-controlled creep, whereas the Cu/Ti-6Al-4&#xa0;V interface showed the lowest displacement (~ 121&#xa0;nm) and the highest stress exponent (<i>n</i> ≈ 3.2), consistent with dislocation-controlled creep. These observations together with microstructural analysis indicate that the Cu interlayer suppresses a continuous Ti/Al IMC layer and instead promotes a thin Cu-rich mix zone and refined interface grains, thereby raising local stiffness/hardness and shifting the dominant creep mechanism toward dislocation-controlled flow. Therefore, Cu-interlayer laser welding provides a microstructure-informed route to engineer Al/Ti joints with improved creep resistance at the critical interface.</p>

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Enhancing the nano-mechanical properties and creep resistance of dissimilar AA7075/Ti-6Al-4 V weldments using a Cu interlayer in laser beam welding

  • 期刊论文

  • 发表日期：

    2026年3月17日

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  • Asim Iltaf,
  • Shayan Dehghan,
  • Noureddine Barka,
  • Rafiq Ahmad

摘要

Dissimilar laser welding of AA7075 aluminum and Ti-6Al-4 V titanium alloys is promising for lightweight structures, but the formation of brittle Ti/Al intermetallic compounds (IMCs) can degrade local mechanical integrity and creep resistance. This work evaluates whether introducing a copper (Cu) interlayer during laser beam welding can enhance the local nanomechanical response and room-temperature nanocreep behavior of AA7075/Ti-6Al-4 V joints. Butt welds were produced using a 380-µm Cu foil, and depth-sensing nanoindentation was applied to map nanohardness, elastic modulus, and indentation creep across the AA7075 heat-affected zone (HAZ), fusion zone (FZ), mix zone, and the Cu/Ti-6Al-4 V interface. Atomic force microscopy was used to characterize indentation-induced surface relief. The Cu interlayer increased nanohardness from 1.37 GPa in the AA7075 HAZ to 5.81 GPa at the Cu/Ti-6Al-4 V interface and increased elastic modulus from 64.1 to 73.2 GPa. The maximum creep displacement (~ 176 nm) occurred in the AA7075 HAZ with n ≈ 2.1, indicating grain-boundary-controlled creep, whereas the Cu/Ti-6Al-4 V interface showed the lowest displacement (~ 121 nm) and the highest stress exponent (n ≈ 3.2), consistent with dislocation-controlled creep. These observations together with microstructural analysis indicate that the Cu interlayer suppresses a continuous Ti/Al IMC layer and instead promotes a thin Cu-rich mix zone and refined interface grains, thereby raising local stiffness/hardness and shifting the dominant creep mechanism toward dislocation-controlled flow. Therefore, Cu-interlayer laser welding provides a microstructure-informed route to engineer Al/Ti joints with improved creep resistance at the critical interface.