Microstructures and mechanical properties of an Al-Cu-Li-Mg-Zr alloy containing Zn and Mn

An AI-3.43Cu-1.28Li-0.49Mg-0.12Zr containing 0.62Zn and 0.29Mn was designed and the microstructures and mechanical properties of the alloy with various heat treatments were investigated. The precipitates of the alloy consist of T1 (Al2CuLi), theta' (Al2Cu), a (Al5Cu6Mg2) and delta' (Al3Li). As solution temperature is changed from 485 degrees C to 530 degrees C, the solution degree of alloying elements in alloy increased, the amount of T1 in the alloy aged at 160 degrees C for 18 h increased and that of theta' is decreased, resulting in an increase of strength. After solution treatment at 530 degrees C, the alloy aged for 18 h at 145 degrees C is mainly strengthened by G P zones, and a little amount of T1 precipitates. As aging temperature is increased to 160 degrees C and 175 degrees C, the strength increased, due to the sufficient precipitation of sigma and T1. The smaller amount of T1 in the alloy aged at 190 degrees C is consistent with its lower strength. Meanwhile, it is found that the a precipitate does not coarsen as aging temperature increases in the range from 160 degrees C to 190 degrees C.