Abstract
Using Al-Zn alloys and pure Zn as a filler metal, we attempted to solder high strength aluminum alloys containing magnasium of more than 2.5% with the aid of ultrasonic vibration. The filler metal potency to solder the aluminum alloys was evaluated and a new soldering process was developed to increase the tensile strength of the joint. The following results were obtained.
Although the aluminum alloys can be soldered with the Al-Zn alloy filler metals, the soldered joints does not have high tensile strength because of the grain boundary segregation of silicon in the filler metal and formation of voids in solederd layer.
When pure zinc is used as a filler metal, soldering during isothermally holding causes the grain boundary segregation of magnesium which results from the base metal dissolution into the filler metal, and leads to decreasing the tensile strength of the joints. However, applying ultrasonic vibration during cooling stage reduces the dissolution of the base metal and suppresses the grain growth of α and β phases, followed by increasing the tensile strength of the joints.
It was revealed that ultrasonic vibration apparently promotes the eutectic reaction between a base metal and a filler metal.
