Microstructure evolution of Ni, Cr, Al-TaC in situ composite directionallysolidified under a high temperature gradient

The effect of solidification rate on the solidified structure, solute segre gation and microstructures such as TaC rods volume fraction, TaC rods avera ge spacing, TaC average transverse area and gamma' phase were experimentall y investigated under a high temperature gradient by employing a method of d irectional solidification with liquid metal cooling. Three types of the sol idified structure were identified: planar, cellular and dendritic. Both sol idified structure and solidification rate had an effect on the eutectic mor phologies. The TaC rods volume fraction could be changed with increasing so lidification rate. TaC average inter-rods spacing and TaC average transvers e areas decreased, the PS (parameter of shape) of gamma ' tends to one and the size of gamma ' phase decreased with increasing solidification rate. (C ) 2001 Elsevier Science S.A. All rights reserved.