The effect of the hypercooling limit on the crystal growth velocity

Patrick Fopp, DLR, Köln, Germany

We applied the electrostatic levitation technique in order to study the crystal growth velocity v as a function of the undercooling ΔT for the intermetallic, congruently melting binary alloy NiTi and the glass forming alloy CuZr, as well as for the Zr-based ternary alloys Zr50Ni50-xCux (x: 30, 35) and the Ni-based ternary alloy Ni50Ti25Zr25. \ The achieved undercoolings are sufficient for the melt to pass through the so-called hypercooling limit ΔT_hyp. \ For all investigated systems, which exceed the hypercooling limit ΔT_hyp, we reproducibly observe a kink in v(ΔT) at ΔT_hyp! Our results could make a valuable contribution concerning an extension of dendrite growth theory to undercooling temperatures ΔT>ΔT_hyp. \ The scatter of our velocity data is smaller than measurements performed by former works due to our experimental setup, which allowed precise triggering at a specific undercooling, and our analysis method, which considered the respective solidification morphologies.

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Session T1: Tuesday, 26 June 2018

Start: 12:45 p.m.
End: 13:00 p.m.