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

Abstract

The effects of aging treatment on the high temperature mechanical properties of cast Al–2Li–2Cu-0.5Mg-0.15Sc-0.15Zr-0.05Ti alloy were investigated. Different test temperature (25 °C, 175 °C, 200 °C, 225 °C) and aging time (aging for 8 h, 32 h, 64 h at 175 °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 °C to 225 °C, the δ′(Al3Li)-Precipitation Free Zone (δ′-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 °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 °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 δ′(Al3Li) phases. The alloy aged for 64 h exhibiting excellent high-temperature performance at 225 °C, which the yield strength reached 302 MPa, the tensile strength reached 312 MPa and the elongation reached 4.4%. The results indicated that δ′-PFZ widening, precipitation strengthening and dynamic recrystallization were the main factors which influenced the high temperature mechanical properties of Al–Li–Cu alloy.