K. Nogita et Ak. Dahle, Eutectic solidification in hypoeutectic Al-Si alloys: electron backscatterdiffraction analysis, MATER CHAR, 46(4), 2001, pp. 305-310
Nucleation and growth of the eutectic, in hypoeutectic Al-Si foundry alloys
has been investigated by the electron backscatter diffraction (EBSD) mappi
ng technique using a scanning electron microscope (SEM). Sample preparation
procedures for optimizing mapping have been developed. To obtain a suffici
ently smooth surface from a cast Al-Si eutectic microstructure for EBSD map
ping, an appropriate preparation technique by ion milling was developed and
applied instead of conventional electropolishing. By comparing the orienta
tion of the aluminum in the eutectic to that of the surrounding primary alu
minum dendrites, the growth mechanism of the eutectic can be determined. Tw
o different results were found, in isolation or sometimes together, but dis
tinct for different strontium contents: (1) crystallographic orientations o
f aluminum in eutectic and surrounding primary dendrites are identical, and
(2) wide variation in orientations of the aluminum in the eutectic. (C) 20
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