LAUSR

The present study was performed on A356 and A413 alloys in non-modified and Sr-modified conditions. To these alloys, pure rare earth (RE) metals, mainly lanthanum (La) and cerium (Ce), were added in the amount of 1 wt% each, individually or combined. The results showed that the addition of 2% RE leads to a significant reduction in the grain size (~ 60%) compared to the base alloy. However, it also leads to precipitation of a large amount of insoluble intermetallics (~ 10% in volume fraction). These intermetallics cause a significant decrease in the alloy ductility and hence deteriorate the tensile properties and impact energies. In addition, Sr may also cause destabilization of the RE intermetallics with possibility of partial dissolution during solution heat treatment. The RE metals have an affinity to react with Sr leading to partial demodification of the eutectic Si. They also react with Cu, diminishing the alloy response to age hardening. The RE intermetallics act as crack initiation sites, leading to premature failure of the sample. The combined occurrence of these various effects complicates the prediction of the alloy behavior.