Abstract
In this work,the effect of Cu addition and heat treatment schemes on the microstructural evolution,mechanical properties,and corresponding strengthening mechanism of cast Al-Li-Mg alloy were investi-gated.Results indicate that the dendritic segregation would be induced after the introduction of Cu,and a well-designed two-stage solution treatment could effectively dissolve secondary phases.With Cu addi-tion,aging hardening responses of the alloys were accelerated,accompanied by a continuous increase in the volume fraction of both S'-Al2CuMg and Al3Li phases,which enhanced the precipitation strengthen-ing effect.Furthermore,in Cu-containing alloys,both the coarsening of Al3Li phases and the expansion of Al3Li-precipitation free zones(PFZ)were inhibited during the aging process.However,severe strain accumulation was found at the interface between the coalesced S'phase and α-Al matrix,which reduced the ductility of the alloy.A good combination of strength and ductility(YS=308 MPa,UTS=428 MPa,EL=5.0％)was obtained in the Al-2.5Li-2Mg-1Cu-0.12Zr alloy aged at 175 ℃ for 32 h due to the nar-rowed Al3Li-PFZ and the synergistic strengthening of Al3 Li and S'phase.This work is expected to provide guidelines for designing novel cast Al-Li alloys with wider applications.
NETL
NSTL
万方数据