Friction stir welding is an ideal technique for welding dissimilar materials compared to

conventional welding methods. However, the main challenges faced during friction stir

welding of different materials are defects and intermetallic compounds formed at the

interfacial region. The tool's penetration into the bottom plate is vital to avoid the defects

formed during the process. When it comes to welding aluminium and steel using the

butt-welding technique, the position of plates on the retreating side and the advancing

and percentage of insertion of the pin into the steel plate are the two critical things that

define the weld quality. In this book, we present insights related to technical challenges

faced during the welding of aluminium and steel and how to overcome them.