Effect of Weld Parameters on the Microstructure of Aluminum-Copper Joints Produced by Flash Welding

The effects of operational conditions on dissimilar Al-Cu flash welded joint quality have been studied using a series of industrial welding experiments. Macro- and microstructural analyses of dissimilar aluminum-copper joints produced by flash butt welding are performed in the present work. Various process conditions including standard and non-standard operational conditions were assessed during the welding experiments. Optical and scanning electron microscopy and electron dispersive x-ray spectroscopy are used to investigate and assess the metallurgical joints created through this process. For suboptimal process conditions, voids (5 mm wide, 1 mm deep) were observed at the joint interface. Some of the voids contained remnants of molten metal while some were empty. Al-Cu intermetallic compounds at the joint area were investigated, and their chemical compositions are determined. The profile of the joint interface was observed to be wavy which is attributed to the voids on the copper side and insufficient material flow of the copper during the upset. The effects of welding parameters on the waviness of the interfaces are investigated. The results show that the waviness of the interface increases with increasing the heat intensity (heat/joint area). No correlation was observed between the flashing speed and the waviness of the interfaces.