Crystal growth in the bulk-metallic-glass Zr-based alloys by using the DC + AC levitation method

Abstract

A levitation method using the alternating and the static magnetic fields suppresses convection in a levitated melt and consequently enables us to measure crystal growth velocity as low as 0.5 mm/s in the undercooled melt. Crystal growth velocities of the constituent phases in the bulk-glass-forming Zr-Ni-Al and Zr-Cu-Al alloys were measured. The growth velocities at the bulk-glass-forming compositions in the Zr-Ni-Al and the Zr-Cu-Al alloys were as low as 1mm/s even if the undercooling exceeded 100K. The interface kinetics and the solute transport of rejected elements resulted in the low growth velocities. The BMG formation in the metal mould casting can be explained by considering the competition between the crystal growth and the glass transition. © 2009 IOP Publishing Ltd.