Microstructure and mechanical properties of 4045/3003/4045 aluminum alloy clad sheet fabricated by vertical-type high-speed tandem twin-roll casting

4045/3003/4045 aluminum alloy clad sheets having the same thickness (6.0 mm) and clad ratio (12 %) were fabricated both by hot roll-bonding and vertical-type high-speed tandem twin-roll casting. Figure 1 shows a schematic illustration of the vertical-type high-speed tandem twin-roll caster. The clad sheets were cold-rolled to 0.17 mm in thickness, annealed at 400°C for 2 h, cold-rolled to 0.10 mm in thickness and finally subjected to heat treatment for brazing at 600°C for 3 min. Figure 2 shows an illustration of the process flow. Microstructures and mechanical properties of the clad sheets were investigated in each stage. Figure 3 shows SEM-BEI images of the cold-rolled sheets fabricated by (a) hot roll-bonding and (b) twin-roll casting. Magnified view near the interface in (a) and (b) is shown in (c) and (d), respectively. Al-Mn dispersoid particles in the core (A3003) and Si particles in the overlay (A4045) of the cold-rolled sheet with 0.17 mm thickness originating from the twin-roll casting were smaller than those originating from the hot roll-bonding. Interfaces between the core and the overlay were clearly observed in the twin-roll casting sheets. Figure 4 shows grain structure of the clad sheets after annealing. A fully recrystallized structure was observed after annealing in the sheet originating from the hot roll-bonding, while the fibrous structure still remained in the sheet originating from the twin-roll casting. Figure 5 shows stress-strain curve of the annealed clad sheets (thickness: 0.17 mm). Yield strength, tensile strength and elongation of the annealed sheet originating from the twin-roll casting were higher than those originating from the hot roll-bonding. Figure 6 shows stress-strain curves of the clad sheets after heat treatment. After the heat treatment for brazing, the tensile strength was the same in both clad sheets.