To compare the effect of Sc modification on fluidity, it is important to quantify
the modification of eutectic silicon. The mean shape factor (S) was used to represent
the eutectic silicon modification level and the appearance probability of plate-like
eutectic silicon. This technique has been previously used by other investigators
[6,15,16]. If the mean shape factor is small, it implies that the eutectic structure
is plate-like. The mean shape factor is calculated as follows: