Fracture of thin cast slabs of Al–Sn alloys during cold rolling

Al 19%Sn 1%Cu (SAE 783) and Al 12%Sn 2.5%Si (SAE 788) alloys are ductile triboalloys which are produced by thin-slab casting followed by cold rolling. For SAE783, rolling defects are rare and generally associated to gross defects in the cast microstructure. SAE 788 forms the metastable β-AlFeSi phase, creating a brittle network within the microstructure. Heat treatment of the as-cast slabs allows reducing the effect of this phase by a reduction in its volume fraction and a change of composition, but this is a slow process. Instead, modification of the casting procedures, according to well-established rules for the production of sound aluminium castings, together with the use of base material of higher purity were shown to be equally efficient in the prevention of rolling defects. The heat treatment could then be omitted while rolling defects were eliminated.