THE METAL MELT STATE EFFECT ON THE MONOCRYSTAL GROWTH N.M. Kochegura, Institute of Foundry Problems, Ukrainian National Academy of Sciences, Kiev, Ukraine.

The work is devoted to the study of the influence of the state of high temperature resistant nickel melt on the monocrystal growth in the compound Ni-Cr-Mo-Ti-Al-Co-Nb-C system. The monocrystal structure was formed in directionally solidified process by Bridgeman- Stockbarger's method. Monocrystal specimens were grown from ordinary or homogenised at 2000-2020 K melts. The monocrystals had a dendritic branch which was grown from crystal nuclear-seeding along the direction <001>. The specimens which was grown from the ordinary melt had a dendrite structure with different irregular intervals between branches. There were "mat spot" on periphery. This "spots " had structure with small equalaxis crystal. The specimens grown from homogenised melts had structure <001> without psevdograin. In this case dendrite cross-section had the regular form. The dendrite axis' and iteraxis space didn't differ neither in size nor in the configuration at the centre as well as at the periphery of the specimens.

These results may be explained thus the homogenised melt creates favourable conditions for the monocrystal growth mostly due to the decrease the deactivation of crystal nucleuses and cluster decays of such metals as W, Mo, Nb, etc.