The metallographic specimens for microstructural analysis
were cut from the same cross-section of the as-cast bars. The
specimens were embedded, mechanically polished and chemically
etched using 50% aqua regia aqueous solution (5 ml HNO3þ15 ml
HClþ20 ml H2O). The solidification structure images of as-cast
specimens with different Ti contents were recorded using an optical microscopy (OM, Neophot21). With the aid of the Image Pro
Plus (IPP) analysis software, the area of each complete grain in the
images was measured and the grain size defined as the equivalentarea circle diameter was determined