Rapid crystal growth in undercooled FeNi melts

Abstract

Dendrite growth velocities have been measured as a function of undercooling ΔT on levitation undercooled Fe 1− x Ni x melts of different concentrations ( x = 0.30, 0.25). The growth velocities have been determined by measuring the recalescence times during crystallization by a high-speed photosensing device. The dendrite growth velocity V increases like a power law with undercooling ΔT up to a critical undercooling ΔT ∗. In this range the experimental data can be described within current theory of dendrite growth, when supposing primary crystallization of the f.c.c. phase. The transition at ΔT ∗ to a weaker linear temperature dependence can be correlated to a grain refinement process.