Development of an 8090/3003 bimetal slab using a modified direct-chill casting process

•Fabricating an innovative 8090/3003 bimetal material by DC casting method.•The 3003 serves as the heterogeneous nucleating substrate for the 8090 side.•The interface bonding strength is higher than the strength of 3003 alloy.•The T6 treatment can strengthen the two parts and interface of the bimetal slab. A modified direct-chill (DC) casting method was used to prepare an 8090/3003 bimetal slab of aluminum alloys with consistent mechanical properties. The interface of the as-cast bimetal material was free of detrimental intermetallic compounds, which indicated excellent metallurgical bonding. A diffusion layer with an average thickness of approximately 80μm was obtained due to the interdiffusion of Li, Mg, Cu and Mn at the bimetal interface. The average ultimate tensile strength of the as-cast bimetal slab was 101MPa, and all fractures occurred on the side of the softer 3003 alloy. T6 treatment was performed on the bimetal slab to investigate the response of the slab to heat treatment. The Vickers hardness of the 8090 side increased by 30% after T6 treatment, reaching 153 HV. The Vickers hardness of the interface layer also increased from 70 HV to 89 HV. The solution strengthening was considered to make the primary contributions on the hardness improvement of the bimetal slab at the interface after T6 treatment.