The vertical-type tandem twin-roll caster is able to produce clad strips from molten alloys by single step. The caster consists of two twin roll casters arranged vertically. The base strip produced at the upper caster is led to the roll gap of the lower caster and the solidifying shell of the overlay alloy grown from the roll surface of the lower caster sandwiches the base strip and produced the clad strip. In the present study, a three-layered aluminum alloy clad strip of A4045/A3003/A4045 was fabricated. Microstructure observation and composition analysis under various magnifications from the optical microscopic-to transmission electron microscopic-order were performed. Both OM and SEM observations found fine solidification structure of both alloy strips. The joint interface was flat and no alloyed region was observed at the interface. A thin layer of about 1μm in thickness including neither Al-Mn base nor eutectic Si particles, was observed at the joint interface. Orientation analysis and chemical composition measurement using TEM and STEM-EDS revealed that the crystal orientation of thin layer took over that of each grain of A3003 and the composition was comparable to the α-Al matrix of A4045. This indicates that the thin layer was the solidified shell of A4045 grown epitaxially from the strip surface of A3003.
