钇粉对 LZ91 与 6061 异质金属超声波焊接的影响

To enhance the quality of ultrasonic-welded joints between LZ91 Mg-Li alloy and 6061 Al alloy, this study investigated the effects of yttrium (Y) powder on the microstructure, welding temperature, and mechanical properties of joints incorporating zinc (Zn) foil interlayers. Experiments conducted at 1500 J welding energy, 0.5 MPa pressure, and 10 μm amplitude demonstrate that the addition of yttrium powder increases the peak welding temperature from 361.7 to 408.9 ℃ and extends the high-temperature duration from approximately 0.6 to 1.0 s. The maximum tensile load of the welded joints improves from 1512.01 to 1577.61 N, representing a 4.3% enhancement compared to joints without yttrium. Microstructural analysis reveals that on the magnesium-zinc interface (LZ91 side), voids form in the zinc foil with yttrium particles aggregating in the pits. A planar Mg₁₂YZn intermetallic compound (IMC) layer is developed on the zinc foil, connecting to the LZ91 alloy through an α-Mg(Zn, Y) solid solution. This Mg₁₂YZn layer suppresses the formation of the typical MgZn₂ IMC at the interface. On the aluminum-zinc interface (6061 side), micro cracks appear in localized regions of the zinc foil. The zinc foil morphology transitions from wavy to partially fragment at the aluminum-zinc boundary. The originally isolated island-like Al-Zn IMCs transform into a continuous Al-Zn solid-solution IMC layer.