The effects of scandium on A356 aluminium alloy in gravity die casting

Abstract

In this project, the addition of scandium into A356 aluminium alloy was studied for its effect on the mechanical properties as well as the changes in microstructure and eutectic morphology after casting process. Scandium addition was administered at the weight percentages of 0·2, 0·4 and 0·6. The results obtained in this work revealed that scandium can significantly enhance the mechanical properties of A356 alloy in terms of hardness and tensile strength. In general, the addition of 0·4 wt-% scandium in A356 alloy was found to be able to achieve the maximum tensile strength of 119·48 MPa as compared to 91·36 MPa for sample without scandium. Similarly, the sample with 0·4 wt-% scandium attained the maximum hardness of 20·36 HRA as compared to 17·32 HRA for unmodified A356. The mechanism that renders the enhancement in mechanical properties can be attributed to grain refinement. In SEM micrographs of samples with scandium, grain refinement can be observed in the microstructure and the morphology of eutectic structure. The eutectic morphology was also converted into a finer and fibrous structure.