Semisolid strip casting using a twin roll caster equipped with a cooling slope

Abstract

A356 aluminum alloy was subjected to semisolid strip casting, a type of rheocasting, by use of a melt drag twin roll caster (MDTRC) equipped with a cooling slope. Equipment and operation are very simple; copper rolls were employed, and, in order to increase cooling rate, no lubricant was used. The produced strip did not stick to the roll. Molten metal became semisolid after flowing down the cooling slope, assuming a solid content of 5–10%. The strip was successfully cast from semisolid slurry at speeds ranging from 30 to 90 m/min; i.e., casting speed was improved by the effect of semisolid casting. Strip thickness was 2–2.5 mm. After rolling and heat treatment, tensile strength was 270 MPa and elongation was 18%. After annealing, the strip was not broken when subjected to a 180° bending test. The mechanical properties of the strip were enhanced by semisolid strip casting. In the middle thickness of the strip, primary crystals were spherical rather than dendritic, and had a size smaller than 50 μm. Eutectic Si was smaller than 5 μm.