The Effect of Cerium and Zirconium Microalloying Additions on the Microstructure and Mechanical Properties of a Novel Al–Cu–Li Alloy

Abstract:

Effects of Ce and Zr microalloying additions on the microstructure and tensile property of novel Al–5.8wt% Cu–1.3wt% Li alloys with an elevated Cu/Li ratio were investigated comparatively by microscopy methods and tensile tests. The microstructural observation showed that the intermetallic dispersoid was significantly refined from coarse polygonal shape to fine irregular particle with combinative addition of Ce and Zr compared to single addition of Ce or Zr. Due to the refinement and modification of intermetallic dispersoid， the fracture mode changed from brittle intergranular fracture to ductile transgranular fracture during tensile. In addition, microstructural analysis revealed that the addition of Ce promoted the precipitation of the T1 phase which was the predominant strengthen phase in Al-Cu-Li alloy. In comparison to Ce containing Al-Cu-Li alloy, Ce Zr-containing Al-Cu-Li alloy has raised the degree of supersaturation of Cu in matrix attributed to less Cu atom had been trapped in finer AlCuCe dispersoid after solution treatment. Thus it was found that the ultimate tensile strength (UTS) and yield strength (YS) increased by 19.6% and 16.1% respectively and with almost similar elongation (El), attributed to decreasing of the phase size, changing of precipitation type to T1 phase only and further grain refinement in Ce Zr-containing Al-Cu-Li alloy.

Key words:Al-Cu-Li alloy; cerium; precipitation; dispersoid; microstructure