Figure 7 illustrates the macrostructure of the directionally solidified sample. It shows the long, welldeveloped columnar grains extending along most of the sample’s length. The grains are approximately 1/8 to 1/4 inch (3–6.4 mm) in diameter at a location of about 3 to 4 inches (75–100 mm) above the water-cooled chill. The grain diameter increases from the bottom of the casting to the top in a fashion that is very typical of directionally frozen castings.