Solidification behavior and elimination of undissolved Al2CuMg phase during homogenization in Ce-modified Al–Zn–Mg–Cu alloy

Abstract

The solidification behavior and intermetallic phase evolution during homogenization annealing of an Al–Zn–Mg–Cu alloy with 0.12 wt% Ce addition were examined. The residual Al2CuMg phase is completely dissolved after homogenization and is replaced by a large number of dispersed micro/nanoscaled AlCuCe enrichment phases within Al matrix. This change occurs because of the formation of a large number of finer lamellar eutectic network structures which are more easily dissolved into Al matrix during the homogenization process. In addition, the trapping of Cu atoms in the stable AlCuCe phase also prevents the formation of Al2CuMg phase, leading to the complete dissolution of Al2CuMg phase in the Al–Zn–Mg–Cu alloy. The grain refinement behavior in Al alloy with Ce addition is similar to that in alloys with the addition of Sc, because of the formation of primary Ce-enriched Al11Ce3 phase as the nucleation agent of α(Al) during solidification.