Al–Si A413 treated and untreated alloys were cast and poured at approximately 720 oC, 700 oC, and 680 oC in a cooling slope to obtain the semisolid material feeding the ceramic nozzle (150 cm3) at the lower roll (single-roll melt-dragged processing)—this drags the metallic slurry via the chill/columnar layers at a rate of 0.2 m/s, forming a molten-metal strip with a thickness of 2 mm and width 45 mm, approximately. The untreated alloy poured at 720 oC formed coarse structures of α-Al dendrites, as well as a coarse eutectic of Al–Si and microshrinking on the surface of the casting strip facing the atmosphere. The Al–Si 413 alloy poured at 680 oC and treated with Al5Ti1B (0.1%) led to microstructural refinement, resulting in α-Al globular structures, the absence of microporosities on the surface facing the atmosphere, and a finer and more homogeneous distribution of the eutectic grains with smaller Si particles. The AlTiB master alloys are not used as a grain refiner in Al–Si alloys because of Si poisoning. This subject is discussed in this paper. The addition of the inoculant and 0.2% of the Al–Si eutectic morphology modifying agent (Al–10%Sr) refined both the α-Al and eutectic phases more efficiently in the cast strip poured at 700 oC and 680 oC. This suggests that the inoculant did not interfere with the action of the modifying agent. As a result, molten metal strips of higher mechanical strengths and ductilities were obtained.
Recycled Al–Si (9.2%) alloy contaminated with Fe (0.3%), Pb (3.1%) and Sn (11.4 %) was cast and poured at 650 oC, approximately 50 oC above the liquidus line. A cooling slope was used to obtain a semisolid material that feeds a ceramic nozzle designed to function as a good contact area for solidification and improve the quality of strip casting. The internally cooled material rolls in soluble oil (1 oil / 9 water) at a rate of 0.2 l/s and works as a heat exchanger which drags the metallic slurry puddle generated at the roll surface at a speed of 0.12 m/s. This forms a metallic strip with a thickness of 2 mm and a width varying from approximately 45 mm to 60 mm. The cooling system of the rolls, combined with four springs placed at the housing screw, prevented adhering of the metallic strip during production at a pressure of approximately 450 N. Cracks were observed on the strip surfaces; however, these defects did not interrupt the continuous flow of the solidified strip during manufacturing. The strip’s poor surface quality could be related to the Pb and Sn contamination as well as cold cracks due to the low pouring temperature. Al-Si eutectics positioned at a grain boundary of α-Al globular structures, as well as the presence of a Sn phase, resulted in a metallic strip with a yield stress, maximum stress and elongation of 94.5 MPa, 100.2 MPa and 1.6%, respectively.
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