In this study, hypoeutectic AlCu5 alloy and AlCu25 alloy in the as-cast condition were severely plastically deformed by extrusion combined with reversible torsion (KoBo) method to produce ultrafine grained structure. Scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM) were used for microstructure characterization. Tensile test for characterization of mechanical properties were also performed. Tensile test were carried at room temperature and at temperature of 100°C and 200 °C, with a speed of 10-4s-1. The results shows, that the KoBo deformation allows refinement of hypoeutectic structure. Tensile tests performed at room temperature revealed, that ultimate tensile strength (UTS) were 223 MPa and 366 MPa for AlCu5 alloy and AlCu25 alloy respectively. For AlCu5 alloy and AlCu25 alloy deformed at 200°C, the UTS were 100 MPa and 182 MPa respectivelly. The elongation for failure (At) for AlCu5 alloy and AlCu25 alloy at room temperature were 18% and 5% respectively. For samples deformed at 200°C, the At were 29% and 40% respectively.Keywords: Al-Cu alloy, severe plastic deformation, KoBo, ultrafine-grains, STEM
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