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

Here we present recent progress on alpha-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 degrees 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 degrees 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 alpha-Al dendrites by varying the ultrasonic time. The shear strength of the alpha-Al dendrite-reinforced joints is improved significantly, with the maximum shear strength approaching 60 MPa. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.