Effects of Rare Earth Er on the As-cast Microstructure of 7055 Aluminum Alloy

The influence of rare earth Er additionits (mass ratio was 0%-0.3%) on 7055 aluminum alloy as-cast microstructure were studied by OM, SEM, EDS, XRD and microhardness testing. The results show that the effect of microstructure refinement heightened with the increasing of Er addition when Er addition was less than 025wt%. The effect of grain refinement was most obviously when Er addition was 0.25wt%, and it was 60% of the grain size without Er. Grain refinement weakened when Er addition was more than 0.25wt%. The compounds of Al8Cu4Er and a small quantity of Al3Er formed and distributed along grain boundaries after Er added to alloy.