Effect of Current Input Method and Solid Fraction on the Roundness and Mechanical Properties in Semi-Solid Processing of Aluminum Materials

The automobile industry has been concentrating on developing eco-friendly materials that improve the safety and fuel efficiency of automobiles. Aluminum alloys, well known as lightweight materials, have been studied, particularly as the demand for high-strength and lightweight materials has been increasing. This study focuses on the technique of rheocasting using electromagnetic stirring (EMS), which is a typical semi-solid method for manufacturing aluminum products. Focusing on EMS, the effect of current input methods on the castability, roundness, and mechanical properties of products manufactured by rheocasting was evaluated. A large electromagnet was used to stir the molten metal, with a maximum weight of 5 to 20 kg of molten metal used in industry, using two types of current input methods-direct current (DC) and alternating current (AC). The microstructure, roundness, and mechanical properties were evaluated by fabricating a tensile specimen using EMS experimentation. The experimental results showed that excellent castability appeared at solid fractions of 20 and 30%. In addition, when the products were manufactured with a solid fraction of 20% and an AC input, the apparent tensile strength was the highest at 177 MPa. The equivalent diameter of the alpha-Al particles was 53 mu m and the roundness was 1.8.