Effects of Cu and Si Contents on the Fluidity, Hot Tearing, and Mechanical Properties of Al-Cu-Si Alloys

The effects of the Cu and Si contents on the fluidity, hot tearing, and mechanical properties of Al-Cu-Si alloys were investigated to evaluate the castability of these widely used forged alloys. Al-Cu-Si alloys with 3.5, 4.5, and 5.5 wt pct Cu and 0, 1.5, and 3.0 wt pct Si were cast at 700 °C in spiral and hot tearing test molds to determine the fluidity and hot tearing characteristics, respectively. With a higher Cu content, the fluidity length decreased by 4.9 and 14 pct, but the hot tearing susceptibility increased from 0.44 to 0.56 and 0.67. With a higher Si content at a fixed Cu content of 4.5 wt pct, the fluidity length increased by 11 pct, and hot tearing was not observed. A solid solution heat treatment was performed at 515 °C for 2 hours and at 525 °C for 8 hours, and the alloy was then quenched in water. Artificial aging was carried out at 185 °C for times of 4, 6, 8, and 10 hours. To improve the fluidity and mechanical properties, 0.10 wt pct Ti was added as a grain refiner. The fluidity increased by 4.6 pct, and the tensile strength increased by 339 MPa.