Microstructure Evolution of a Novel Al–Cu–Li–Ce Alloy During Homogenization

Abstract:

The present work aims to clarify the formation of the ?1(Al8Cu4Ce) phase and its formation mechanism in the high Cu content alloy with Ce addition. The microstructure evolution during the two-step homogenization annealing process was investigated in the novel high Cu/Li Al–Cu–Li–Ce alloy. The formation of the coarse Ag Mg enriched TB (Al7Cu4Li) phase and the primary AlCuCe phase was found to occur under solidification. Two types of the minor ?1 phases were found to form after homogenization. It is concluded that the ?1 phase nucleation mechanism could involve either nucleation on an existing TB phase by Ce diffusion from the Al matrix or the transformation of the primary AlCuCe phase into the ?1 phase by Ce diffusion through the coarse primary AlCuCe phase shrink. It also can be deduced that the grain refinement is mainly the result of the primary AlCuCe promoting ? (Al) nucleation and further prohibiting the grain growth for the experimental alloy.

Key words:an novel Al-Cu-Li alloy; cerium element; segregation; t₁phase; homogenization