On the fatigue properties of a third generation aluminium-steel butt weld made by Hybrid Metal Extrusion & Bonding (HYB)

•Al-steel HYB butt joint exhibits unique fatigue properties in as-welded condition.•Interfacial cracking is prevented by a high intrinsic Al-Fe bond strength.•Fatigue crack development occurs at the weld toe on the Al side of the joint.•Joint fatigue strength is comparable with that of corresponding Al-Al weldments. The present investigation is concerned with the high-cycle axial fatigue behaviour of a third generation Al-steel butt weld made by Hybrid Metal Extrusion & Bonding (HYB). In this particular weld, metallurgical bonding is achieved by a combination of microscale mechanical interlocking and intermetallic compound (IMC) formation, where the IMC layer is in the sub-micrometre range (