The effect of alloy composition on the microstructure and tensile properties of binary Mg-rare earth alloys

Additions of La, Ce and Nd to commercially pure Mg were made up to similar to 5 wt.%. It was found that the intermetallic phases formed in the eutectic were Mg(12)La, Mg(12)Ce and Mg(3)Nd respectively. Predictions from the Scheil-Gulliver equation correlated reasonably well with the measured volume fractions. The yield strength increased and the elongation to fracture decreased with an increase in the amount of intermetallic phase present in each alloy. The rate of change in mechanical properties was also found to be dependent upon the type of intermetallic, With Mg(3)Nd being more influential than Mg(12)RE. The morphology of the eutectics was also characterised and compared with the predictions based on phase volume fraction. There were some variations from those predictions, which may be due to the high undercooling produced as a result of the fast cooling rates in high pressure die casting.