Phase selection in hypercooled alloys

The effect of the hypercooling limit on the crystal growth velocity v as a function of the undercooling temperature Δ T for intermetallic binary and ternary alloys remains unexplained yet. In combination with the electrostatic levitation technique, we performed in-situ high energy synchrotron X-ray diffraction measurements at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, to investigate the phase formation of the binary alloy NiTi , the Zr -based ternary alloys (NixCu1−x)Zr ( x = 0.3 , 0.4 ) and the Ni -based ternary alloy Ni ( Zr 0.5 Ti 0.5 ) for solidification events at undercooling temperatures Δ T Δ T hyp and Δ T > Δ T hyp , whereas Δ T hyp are the corresponding hypercooling limits of the systems. Our results indicate that the cubic B2-type ( CsCl -type, space group Pm3 m # 221 ) phase is always the primary solidifying phase for all investigated alloys. This holds for all undercoolings obtained. Thus, the deceleration effect observed in the crystal growth velocity for all investigated alloys at their hypercooling limits seems to be caused by something different than the formation of different phases.