스칸듐 첨가에 따른 Al-Si-Cu 합금의 미세조직 및 기계적 특성 변화 연구

Abstract

The effects of scandium addition on the microstructure and mechanical properties of Al-Si-Cu aluminum alloy were investigated. The Al-Si-Cu-Sc alloy were prepared by gravity die casting process. The effects of scandium-added Al-Si-Cu alloys on the mechanical properties were investigated using the metallurgical technique, Vickers hardness test and tensile test. In this study, scandium was added at 0.2 wt%, 0.4 wt%, 0.8 wt%, and 1.0 wt%. T6 heat treatment was performed at 495°C for 4 hours solution treatment and aging treatment at 190°C for 5 hours. The microstructure of Al-Si-Cu alloy with scandium addition changed from dendrite structure to equiaxed structure in the specimens of 0.4 wt% Sc or more, and coarse needle shape Si and β-Al5FeSi phases were segmented and refined. The Al3Sc phase was distributed in the size of 10 nm to 20 nm inside the alloy matrix. After T6 heat treatment, solution heat treatment considerably reduced the size of the eutectic Si phase and the precipitated Al2Cu intermetallic phase increased the hardness of the alloy. The mechanical properties of the Al-Si-Cu-Sc alloys showed improved strength and elongation. The Sc addition and T6 heat treatment of this study, simultaneously induce grain refinement, dispersion strengthening, spheroidization effect, and precipitation hardening effects of Al-Si-Cu alloy. Consequently, their mechanical properties are suitable for high-strength automotive lightweight parts.