DENDRITIC GROWTH VELOCITIES OF THE INTERMETALLIC COMPOUNDS NI2TIAL, NITI, NI3SN, NI3SN2 AND FEAL

The dendritic growth velocities of melts of several ordered intermetal lic compounds were measured during rapid solidification. Bulk melt und ercoolings were achieved by the application of the electromagnetic lev itation and the glass fluxing technique. The results obtained on Ni2Ti Al, NiTi, Ni3Sn. Ni3Sn2 and FeAl allow comparisons with respect to the dependence of the crystal growth behaviour on the complexity of the s uperlattice structure and on the predominant type of bonding. Disorder trapping in FeAl was strongly indicated by the observation of large g rowth velocities up to 7 m s(-1), whereas all other investigated alloy s 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 order ed intermetallic compounds in contrast to collision-limited growth con ditions in pure metals and solid solutions. (C) 1997 Elsevier Science S.A.