where S is the mean area weighted shape factor of the silicon phase; Ai is the
area of a single silicon structure and/or plate; Pi is the perimeter of a single silicon
structure and/or plate, and n is the number of structures and/or plates in a single
field. These parameters were determined from an area with a 1-mm diameter on
each sample. At least 25 points were used at 100× magnification for three pieces
of each alloy to obtain the average results. The mean shape factor (S) of samples
without Sc addition was determined identically except that 10 points were used
rather than 25.