Solidification in alloys begins when the temperature
drops below the liquidus, TL, and is complete
when it reaches the solidus, TSWithin this temperature range, the alloy is in a
mushy or pasty state consisting of columnar dendrites
(from the Greek dendron, meaning “akin to,”
and drys, meaning “tree”). Note the presence of liquid
metal between the dendrite arms. Dendrites have
three-dimensional arms and branches (secondary
arms), which eventually interlock, as can be seen in
Fig. 10.5. The study of dendritic structures (although
complex) is important, because such structures contribute
to detrimental factors, such as compositional
variations, segregation, and microporosity within a
cast part.