Kouji Wada

Effect of bonding conditions on joints of 5052Al and 6063Al in pulsed electric current bonding

Recent reports on sintering and bonding using the pulsed electric current bonding process indicate that the metals are subjected to Joule heating due to the electrical resistance at the contact points. However, the influence of bonding conditions on local heating phenomena and joint quality remains unclear. In this study, the effects of bonding conditions (bonding temperature, pressure, surface roughness, interlayer, electric current wave and so on) on joint efficiency are investigated using 5052A1 and 6063A1 in pulsed electric current bonding. The joint strength of 5052A1 and 6063A1 are improved using 2024A1 as the interlayer between the bonding interfaces. The joints with the 2024A1 powder as the interlayer are stronger than ones with 2024A1 plate, and are as strong as the base metal. The improvements of the joints depend on effective heat generation at the bonding interface due to the electrical resistance. It is 0.08 g (thickness: 0.04 mm), enough for the amount of powder between the bonding interfaces. The dispersion of the powder from the joints does not occur under various conditions. The surface roughness and electric current wave (direct current, duty ratio, pulse frequency) have no effect on the joint strength. With the increase of bonding temperature and pressure, the deformation of the joints increases. Then bonding temperature and pressure have to be selected to prevent a big deformation of joint configuration.

Effects of post heat treatment on 5052Al and 6063 aluminium joints during pulsed electric current bonding

In a previous study, the effects of the bonding conditions (bonding temperature, pressure, surface roughness, interlayer and electric current wave) on joint efficiency were investigated using 5052Al and 6063Al joints during pulsed electric current bonding. The results were found as follows. The surface roughness and current waveform (direct current, duty ratio and pulsed frequency) show no effect on the joint strength. With an increase in the bonding temperature and pressure, the deformation of the joints increase. The bonding temperature and pressure have to be selected in way to prevent significant deformation of the joint configuration. In the current study, the effect of the post heat treatment on the joints is under investigation to improve the joint strength of 5052Al and 6063Al. Post heat treatments the 5052Al and 6063Al joints improve the strength of both of them. The effect of the post heat treatment on the 6063Al joint is larger than the effect on the 5052Al joint. Post heat treatment performed on the joints promoted a Mg reduction mechanism by Al alloys to remove an oxide film at the bond interface. Based on the tensile properties and the microstructure of the joints, an optimum amount of Mg is added in order to improve the joint properties of the Al alloy, which was determined to be 0.3–1 mass percentage. Using a solution and ageing heat treatment, the joint properties of 6063Al equal the joint properties of a base metal.