Age-hardening behavior of a SiCw/Al-Li-Cu-Mg-Zr composite

The age-hardening behavior of a SiCw/Al–Li–Cu–Mg–Zr composite fabricated by squeeze casting method was investigated using Vickers hardness measurement and transmission electron microscopy (TEM). For comparison, the aging characteristics of the unreinforced matrix alloy with an identical processing and aging history were also examined. The results indicate that the composite exhibits an accelerated hardening response compared to the unreinforced matrix alloy at the four selected aging temperatures of 130, 160, 190 and 220 °C. Aging temperature has great influence on the hardening characteristics of the SiCw/Al–Li–Cu–Mg–Zr composite, and the suitable aging temperature range for the provided composite in this paper is 160∼190 °C. TEM observations reveal that the addition of SiC whiskers to the Al–Li–Cu–Mg–Zr alloy can speed up the growth rate of δ′ (Al3Li) precipitates and lead to the early nucleation of S′ (Al2CuMg) phase. The accelerated precipitation of δ′ and S′ phases is proposed to be responsible for the enhanced age-hardening of the SiCw/Al–Li–Cu–Mg–Zr composite.