The effect of cooling rate of solidification on microstructure and alloy element segregation of as cast alloy 718

Abstract

In this study, several solidification cooling rates of alloy 718 were obtained using different pouring and mould temperature combinations. Secondary dendrite arm spacing, grain size and the volume fraction of Laves phase formed at different solidification cooling rate were systematically observed. The relationships of secondary dendrite arm spacing, grain size and volume fraction of Laves phase with the cooling rate were set up by measurement and data treatment. These relationships possess semi-quantitative significance within the condition of this study, which can be used to predict the secondary dendrite arm spacing, grain size and volume fraction of Laves phase when knowing the solidification cooling rate of alloy 718. The extent of effect of the solidification cooling rate on the porosity and the morphology of Laves phase for alloy 718 also were obtained by metallographic analysis. The alloy element distribution in Laves phase and in dendritic core region were measured by energy spectral analyzing electron microscope. Some quantitative conceptions about the relationship of the microstructure with the solidification cooling rate for as cast alloy 718 have been achieved.