Dendritic growth kinetic of Al68.5Ni31.5 under reduced gravity conditions

Abstract

Containerless processing of a metallic specimen offers the potential to directly observe solidification undisturbed by any interaction of the liquid melt with container walls. Since heterogeneous nucleation from containerwalls is completely circumvented it is furthermore realizable to undercool the liquid below its equilibrium melting temperature. On Earth, levitation requires strong electromagnetically fields which however induce strong fluid flow effects (forced convection). This fluid flow affects heat and mass transport and consequently governs the solidification dynamics. Weightlessness on the other hand essentially reduces fluid flow effects so that crystal growth is controlled by intrinsic material-specific transport. In the present experiment Electro-Magnetic Levitation aboard the TEXUS 49 sounding rocket is utilized to measure the dendrite growth velocity of Al68.5Ni31.5.