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Electromagnetic levitation apparatus for investigations of the phase selection in undercooled melts by energy-dispersive X-ray diffraction

: Notthoff, C.; Franz, H.; Hanfland, M.; Herlach, D.M.; Holland-Moritz, D.; Petry, W.


Review of scientific instruments 71 (2000), Nr.10, S.3791-3796
ISSN: 0034-6748
ISSN: 1089-7623
Fraunhofer INT ()
liquid alloys; magnetic levitation; nickel alloys; nucleation; rapid solidification; synchrotron radiation; undercooling; vanadium alloys; X-ray apparatus; x-ray diffraction; zero gravity experiment; electromagnetic levitation apparatus; phase-selection; undercooled melt; energy-dispersive x-ray diffraction; metastable state; metastable phase formation; bulk melts undercooling; synchrotron radiation diffraction; rapid crystallization; undercooled alloys; direct identification; crystalline phases; BCC phase; FCC phase; tetragonal intermetallic phase; nonequilibrium state; undercooling temperature; containerless processing; heterogeneous nucleation; Ni-V

The metastable state of an undercooled melt can provide access to the formation of metastable phases whose crystallographic structures differ from their stable counterparts. The electromagnetic levitation technique is used here to undercool bulk melts without containers. This technique, combined with energy dispersive X-ray diffraction of synchrotron radiation, allows in situ study of the rapid crystallization of undercooled Ni-V alloys. The binary Ni-V alloy was chosen as a model system, because it shows phase competition of three different crystallographic phases, bcc, fcc, and an intermetallic phase of tetragonal structure at intermediate concentrations. The diffraction experiments provide for direct identification of the various crystalline phases formed from the nonequilibrium state of the undercooled melt. The phase selection is investigated as a function of undercooling temperature for Ni-V alloys of different concentrations.