Effect of grain boundary fraction on castability of a directionally solidified nickel alloy

The effect of grain boundary (GB) fraction on hot tearing during directional solidification was explored. The increase of GB fraction was found to reduce the hot tearing tendency. The eutectic melt is finely dispersed and increasingly discontinuous at the GBs when the GB fraction is increased. The change of eutectic melt at the GBs is related to the reduced concentration of GB elements or impurities. The better castability is attributed to the uniform distribution of strain due to the presence of more GBs and the stronger GB cohesion because of the larger bridging areas.