Mechanical degradation of magnetic pulse welded Al–Fe joint in neutral salt environment

Abstract

The urgent need in lightweight of vehicle body promoted the application of multi materials with high specific strength, and this involves the reliable welding of dissimilar materials. In this study, AA5052 aluminum alloy and HC420LA steel were welded by magnetic pulse welding. The mechanical degradation of the dissimilar Al–Fe joint after different salt spray corrosion duration was investigated. The atomic force microscopy-scanning Kelvin probe force microscopy (AFM-SKPFM) and immersion tests were also performed. The fracture of the Al–Fe joint was observed by optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The ultimate shear strength of the Al–Fe joint only declines for 10% after three weeks' corrosion. Crevice corrosion is found in the overlapping region, and galvanic corrosion and stress corrosion occur in the weld region. The corrosion in the flat welding interface is mainly galvanic corrosion due to the high corrosion driving force, while the corrosion in the wave welding interface is mainly stress corrosion.

Keywords

• Magnetic pulse welding
• Dissimilar materials
• Salt spray corrosion
• Galvanic corrosion
• AFM
• Stress corrosion