MICROSTRUCTURE SELECTION IN BINARY AND TERNARY ALLOYS

The solidification conditions of an alloy determine the microstructure obtained and hence the properties of a part. Most metallic alloys can be either dendritic or eutectic, depending on the composition, solidi fication velocity and temperature gradient. For binary alloys there is a model which can be used for the prediction of the coupled zone. It was applied to the Al-Fe system, and the results are in good agreement with experimental observations. The model was extended to dilute tern ary alloys. Phenomenological observation of a typical ternary phase di agram shows that the addition of a small amount of a third element fav ours the dendritic structure to the detriment of the eutectic plane fr ont. An example of a calculated microstructure map is shown for the Al -Fe-Si system.