Dendritic growth velocities of the intermetallic compounds Ni₂TiAl, NiTi, Ni₃Sn, Ni₃Sn₂ and FeAl

The dendritic growth velocities of melts of several ordered intermetallic compounds were measured during rapid solidification. Bulk melt undercoolings were achieved by the application of the electromagnetic levitation and the glass fluxing technique. The results obtained on Ni₂TiAl, NiTi, Ni₃Sn, Ni₃Sn₂ and FeAl allow comparisons with respect to the dependence of the crystal growth behaviour on the complexity of the superlattice structure and on the predominant type of bonding. Disorder trapping in FeAl was strongly indicated by the observation of large growth velocities up to 7 m s^-1, whereas all other investigated alloys solidified chemically ordered even at deep undercoolings up to 300 K. A dendrite growth model was applied to analyse the experimental data. The results reveal the diffusion-controlled growth kinetics of ordered intermetallic compounds in contrast to collision-limited growth conditions in pure metals and solid solutions.