Effect of short solution and artificial ageing on microstructure and mechanical properties of Al-Si-Mg-La-Ce alloy formed by high pressure die casting

With the growing demand for low-carbon economy and automotive lightweighting, the pursuit of aluminum alloys with high strength-toughness has remained unabated in both scientific research and industrial production. In this work, a high strength and ductility of Al-Si-Mg alloy is developed through rare elements (La and Ce) modification and high pressure die casting (HPDC). This novel Al-Si-Mg-La-Ce alloy demonstrates an ultimate tensile strength of 346.5 MPa and an elongation of 8.47 % after short solution at 510℃ for 10 min and artificial ageing at 180℃ for 8 h, which is competitive with other die cast Al-Si alloys. This casted Al-Si-Mg-La-Ce alloy shows fine grains and fibrous eutectic silicon along with high-density twin structure and stacking faults owing to La and Ce modification and high cooling rate brought by HPDC. Furthermore, a short solution treatment achieves eutectic Si spheroidization, promotes Mg element homogenization, prevents gas pore expansion and limits grains growth. The solution treated alloy owns a higher Vickers hardness and electrical conductivity compared with the casted sample, and both reach the maximum value after 8 h ageing at 180℃. Besides, the dispersed Si particles with stacking faults, Al-rich clusters and Mg-containing precipitates are obtained in the final product. Multiple effects contribute to this high strength and high plasticity of Al-Si-Mg-La-Ce alloy, which provides a feasible and practical production method for high performance requirements aluminum alloys.