Structure and properties of carbon steel–aluminium dissimilar joints

Abstract

Carbon steel is joined to aluminium using the ultrasonic brazing method with Zn–Al filler at 663 K, employing different ultrasound application times. Different reaction layers could be observed at the interface, containing compounds such as FeAl₃, Fe₂Al₅, Fe₃Al, and FeAl, and solid solutions such as Fe–Zn and Zn–Al. For shorter ultrasound application times, formation of the aluminium rich Fe–Al compounds occurred; conversely, after longer ultrasound times formation of the iron rich Al–Fe compounds occurred, which improves the joint bond strength. The maximum bond shear strength of 127 MPa was obtained for an Al–steel joint brazed at 663 K with 3 s ultrasound application time. Extending the ultrasound time beyond 3 s caused the formation of FeAl compound, which decreased the joint bond strength; however, the strength of the joints remained at a higher level than that obtained with FeAl₃ and Fe₂Al₅.

Keywords:

• CARBON STEEL-ALUMINIUM JOINTS
• ULTRASONIC BRAZING
• ZN-AL FILLER
• REACTION LAYERS
• INTERMETALLIC COMPOUNDS
• BOND SHEAR STRENGTH