Crystal-melt kinetic coefficients of Ni3Al

Crystal-melt interface growth kinetics of the intermetallic system, Ni3Al, is investigated using molecular dynamics simulation. Kinetic coefficient, one of the important parameters that controls solidification growth morphology, is calculated using free solidification method employing two different interatomic potentials. Compared to pure metals, the kinetic coefficients of the ordered systems are smaller by at least an order of magnitude. For the first time, we show here that the growth kinetics of ordered Ni3Al is very sluggish compared to that of the disordered system. The difference is attributed to the diffusion limited growth in the ordered systems vis-á-vis the interface limited growth in their counterpart. Theoretical models by Broughton-Gilmer-Jackson and Wilson-Frenkel are employed to corroborate the identified growth mechanisms. The extent of disorder trapped increases with increasing interface velocity.

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