| Abstract |
| A 3-ply clad metal consisting of aluminum and copper was fabricated by roll bonding process and the microstructures and mechanical properties of the roll-bonded and post-roll-bonding heat treated Cu/Al/Cu clad metal were investigated. A brittle interfacial reaction layer formed at the Cu/Al interfaces at and above 400℃. The thickness of the reaction layer increased from 12 ㎛at 400℃ to 28 ㎛at 500℃. The stress-strain curves demonstrated that the strength decreased and the ductility increased with heat treatment up to 400℃. The clad metal heat treated at 300℃ with no indication of a reaction layer exhibited an excellent combination of the strength and ductility and no delamination of layers up to final fracture in the tensile testing. Above 400℃, the ductility decreased rapidly with little change of strength, reflecting the brittle nature of the intermetallic interlayers. In Cu/Al/Cu clad heat treated above 400℃, periodic parallel cracks perpendicular to the stress axis were observed at the interfacial reaction layer. In-situ optical microscopic observation revealed that cracks were formed in the Cu layer due to the strain concentration in the vicinity of horizontal cracks in the intermetallic layer, promoting the premature fracture of Cu layer. Vertical cracks parallel to the stress axis were also formed at 15% strain at 500℃, leading to the delamination of the Cu and Al layers. |
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| Key Words |
| heat treatment, interfacial fracture, copper, aluminum, clad |
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