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MM: Fachverband Metall- und Materialphysik
MM 61: Liquid and Amorphous Metals V - Structure and structure formation
MM 61.1: Vortrag
Donnerstag, 3. April 2014, 15:45–16:00, IFW A
Crystal growth behavior of undercooled silicon melts — •Daniel Simons1, Pierre-Yves Pichon1,2, and Dieter Herlach1 — 1DLR, Institut für Materialphysik im Weltraum, 51170 Köln — 2RGS Development B.V., Bijlestaal 54 A 1721 PW, Broek op Langedijk, Netherlands
Electromagnetic levitation technique is used to containerless undercool and solidify pure silicon melts. Due to the avoidance of heterogeneous nucleation on container walls large undercoolings up to 320 K below the melting temperature of pure Si, 1685 K, are achieved. The velocity of the crystal growth is measured as a function of undercooling by recording the propagation of the solidification front with a high speed camera. Maximum velocities of 12 m/s are measured at largest undercooling. The high speed video frames give also information of the morphology of the growth front. Plate-like crystals, isolated dendrites, and smaller dendrites at low, moderate and high undercooling temperatures are observed. The plate like crystals morphology is the result of the faceting of the solid-liquid interface at low undercooling. By increasing the undercooling, the solid-liquid interface roughens at the atomic scale, and metallic-like dendrite growth becomes occurs. This effect is identified as kinetic roughening of a smooth solid-liquid interface.