Microstructure design and dissolution behavior between 2024 Al/Sn with the ultrasonic-associated soldering

Here we present recent progress on α-Al dendrite-reinforced joints of 2024 aluminum produced by the ultrasonic-assisted soldering method. In ultrasonic-assisted soldering of Al2024, pure Sn was utilized as a filler metal, the vibration frequency was 21 kHz, and the temperature was 300 °C. Interestingly, the aluminum content in the bond was up to 3.2 mass%, which is much higher than the solubility limit of aluminum in Sn at 300 °C. The evolution of the microstructure of the aluminum dendrites in bonds with different ultrasonic time was observed to investigate the dissolution behavior of 2024 Al in Sn under ultrasonic conditions. A migration model of aluminum dendrites in the bonds is proposed, which enables control of the extent of reinforcing α-Al dendrites by varying the ultrasonic time. The shear strength of the α-Al dendrite-reinforced joints is improved significantly, with the maximum shear strength approaching 60 MPa.

► α-Al dendrite-reinforced joints produced by the ultrasonic-assisted soldering.
► Dissolution behavior of 2024 Al in Sn under ultrasonic conditions.
► Migration model for the formation of aluminum dendrites in the bonds.