Effect of aging treatment on high temperature mechanical properties of a cast Al-Li-Cu alloy

The effects of aging treatment on the high temperature mechanical properties of cast Al-2Li-2Cu-0.5Mg-0.15Sc0.15Zr-0.05Ti alloy were investigated. Different test temperature (25 degrees C, 175 degrees C, 200 degrees C, 225 degrees C) and aging time (aging for 8 h, 32 h, 64 h at 175 degrees C) were designed for comparison. The results showed that at room temperature, the strength of the alloy improved with the prolongation of aging time. When the test temperature increased from 175 degrees C to 225 degrees C, the delta '(Al3Li)-Precipitation Free Zone (delta '-PFZ) widened from 31.25 nm to 110.83 nm, causing a decrease in strength. In addition, the presence of the dynamic recrystallization at 225 degrees C resulted in an increase in elongation. As the aging time prolonged from 8 h to 64 h, the high temperature strength of the alloy at 225 degrees C decreased first and then enhanced. The improvement of alloy strength aged for 64 h was mainly due to the increase of T1(Al2CuLi), S '(Al2CuMg) phases and the decrease of delta '(Al3Li) phases. The alloy aged for 64 h exhibiting excellent high -temperature performance at 225 degrees C, which the yield strength reached 302 MPa, the tensile strength reached 312 MPa and the elongation reached 4.4%. The results indicated that delta '-PFZ widening, precipitation strengthening and dynamic recrystallization were the main factors which influenced the high temperature mechanical properties of Al-Li-Cu alloy.