Solidification behaviour and the effects of cerium on the intermetallic structure of an novel Al–Cu–Li alloy

Abstract:

In the present work, the microstructure evolution of a novel Al-Cu-Li alloy with rare earth cerium (Ce) additions (0, 0.1, 0.3, and 0.5 wt.%) were investigated. The as-cast samples were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron probe microanalysis (EPMA) with wavelength dispersive spectroscopic (WDS). The microstructural observation showed that the grains were significantly refined with increasing the addition contents of rare earth Ce. A Mg Ag-rich Al₇Cu₄Li intermetallic phase was observed in all experimental alloys except for the alloy with addition of 0.5wt.? that may be attributed to emerged an extra gray CuSi(AgMg) phase. Furthermore, the coarse rodlike Al₂CuLi phase was completely absent with Ce level up to 0.3wt.%. The analysis shows that the Ce addition introduces changes in the precipitation sequence and consequently in the solidification behavior of the alloy. It can be deduced that the grain refinement is mainly the result of the primary Al₈Cu₄Ce promoting a (Al) nucleation and further prohibiting the grain growth for the cerium addition experimental alloys.