Effects of solution treatment on mechanical properties and microstructures of Al-Li-Cu-Mg-Ag alloy

YU Cheng(余成)¹, YIN Deng-feng(尹登峰)¹, ZHENG Feng(郑峰)^{1, 2}, YU Xin-xiang(余鑫祥)¹

(1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Nonferrous Materials of Ministry of Education (Central South University),
Changsha 410083, China)

Abstract:Mechanical properties and microstructures of Al-Li-Cu-Mg-Ag alloy after solution treatments were investigated by means of optical microscopy (OM), tensile test, hardness measurement and electrical conductivity test, differential scanning calorimetric (DSC), energy dispersive X-ray (EDX), scanning electron microscopy (SEM) and transition electron microscopy (TEM), respectively. The results show that both tensile strength and hardness increase first and then decrease with temperature at constant holding time of 30 min with maximum strength and hardness appearing at 520 °C. Tensile strength, hardness and elongation of samples treated at 520 °C for 30 min are 566 MPa (σ_b), 512 MPa (σ_0.2), HB 148 and 8.23% (δ), respectively. There are certain amount of fine T₁ (Al₂CuLi) phase dispersing among Al substrates according to TEM images. This may result in mixed fracture morphology with trans-granular and inter-granular delamination cracks observed in SEM images.

Key words:Al-Li-Cu-Mg-Ag alloy; solution treatment; microstructure; mechanical properties