Microstructure evolution of Ni, Cr, Al–TaC in situ composite directionally solidified under a high temperature gradient

Abstract

The effect of solidification rate on the solidified structure, solute segregation and microstructures such as TaC rods volume fraction, TaC rods average spacing, TaC average transverse area and γ′ phase were experimentally investigated under a high temperature gradient by employing a method of directional solidification with liquid metal cooling. Three types of the solidified structure were identified: planar, cellular and dendritic. Both solidified structure and solidification rate had an effect on the eutectic morphologies. The TaC rods volume fraction could be changed with increasing solidification rate. TaC average inter-rods spacing and TaC average transverse areas decreased, the PS (parameter of shape) of γ′ tends to one and the size of γ′ phase decreased with increasing solidification rate.