Dendritic growth-A test of theory

摘要: Steady-state theories of dendritic solidification are reviewed, and three nonisothermal theories, expressed as simple power laws, chosen for experimental verification. Specifically, the axial growth rate,V, a freely growing dendrite can be asV =βGΔθn, wheren andβ exponent prefactor derived from each theory,G is lumped material parameter, andΔθ supercooling. Succinonitrile, low entropy-of-fusion plastic crystal, was prepared in several states purity test system, studied both usual manner long tubes, novel apparatus which conditions “free” were attained. Kinetic measurements show that only when obtain data reconcilable with current theory form discussed above. In particular, we thatn = 2.6, agreement Nash Glicksman Trivedi; however, prefactorsβ those do not agree value determined succinonitrile, substance whichG known accurately. Tip radius measurements, taken over relatively narrow range supercooling, combined rate prove Peclet number-supercooling relationship steady-state theoriesall experiment. This curious agreement, along inability to “decompose” numbers into acceptable velocity-supercooling tip radius-supercooling relationships explained on basis limitations imposed by assumption itself. Directions future theoretical investigation light findings presented.