Phase transformation studies at the solid/liquid interface by directional solidification of alloy 718

The phase transformation temperatures are especially important in alloy 718 because it requires careful heat-treatment cycles. The DTA method is generally used to estimate the characteristic temperatures of phase transformations. However, DTA is an indirect method to confirm phase transformations, and there are always discrepancies in analyzing the DTA thermograms. In this study, the directional solidification and quenching technique has been applied to estimate the phase transformation temperatures near the solid/liquid interface temperatures by measuring temperatures directly during directional solidification. These phase transformation temperatures were confirmed in the quenched solid/liquid interface. Solidification behavior at the solid/liquid interface with solidification rate and temperature gradient were also discussed.