The AlFeMnSi intermetallics competition in the interdendritic eutectics in AlSi cast alloys influenced by cooling rate and transition metals content

Microscopic observations and quantitative analysis of the microstructure image were used to analyze the solidification course and morphology evolution in polyphase eutectics in the AlSi casting alloys with transition metals Fe and Mn. The utility of the analytical test procedures was demonstrated. It was stated that their precision and repeatability should be improved. Further works on quantitative morphological coefficients used as objective discriminators of the particular morphological form of phase constituents should be continued.
Nevertheless, obtained results of the microstructure image analysis indicated that in a concentration range of transition metals: Fe 0.5-1.5 wt. % and Mn 0-0.5 wt. %, the total Vv of the eutectic intermetallics has increased with a total content of the transition metals (Fe + Mn). In both group of alloys hypo- and eutectic the final results of the competition between phases αc-AlFeMnSi, αH-AlFeSi and β-AlFeSi have been explained as affected by non-equilibrium microsegregation of Fe, Mn and Si in solidifying liquid, and by the actual value of the Fe/Si coefficient. Preferences for αc-AlFeMnSi phase were reinforced by a decrease in the value of Fe/Mn coefficient.

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