Aging behaviors of Al-Cu-Li-Zr alloy containing Sc

Single aging effects on the microstructures and the room-temperature mechanical properties of Al-3.5Cu-1.5Li-0.22(Sc+Zr) alloy were observed using TEM, tensile test and hardness test at room temperature. The results show that the alloy has the character of aging hardening. The aging temperature and aging time have significant effects on the amount and distribution of the major phase of precipitation and strengthening of the alloy. At both high and low temperatures, the precipitation caused by aging is few and coarse, but at high temperature, the coarse equilibrium phases are visible at grain boundaries, therefore, influencing the composite properties of the alloy. The proper artificial single-aging treatment of the alloy is 160℃, 40h. Under this condition, the alloy obtains homogeneously distributed fine T_1 phases, which leads to an optimal mechanical properties, i.e. σ_b is 483MPa, σ_ 0.2 is 413MPa, and δ is 8.4% for the alloy. However, extending overaging to 50h at 160℃, the coarse equilibrium phases precipitate at grain boundaries leads to wide precipitates-free zone(PFZ) along the grain boundaries, further results in a decrease in the composite properties of the alloy.