Characterization Of Solid-liquid Interfacial Energy And Numerical Simulation Of Alloys During Solidification

The solid-liquid interface is an important parameter during solidification,which plays a key role in the nucleation and growth of metal solidification.The research on interfacial energy has always been the focus.At present,a variety of methods have been formed to study interfacial energy through experiments.However.most of the researches focus on the pure metal,and the process to study interfacial energy is relatively complex.In this paper,a simple method to calculate the solid-liquid interfacial energy was proposed.The enthalpy during solidification of the primary phase of the alloy was measured by differential scanning calorimetry(DSC).and the solid-liquid interfacial energy of the primary phase-liquid phase of the alloy was calculated by using Turnbull formula.The calculated results were applied to the microstructural simulation to study the influence of interfacial energy on the microstructural morphology.This paper mainly studies from the following four aspects.(1)Study on primary phase of vermicular graphite cast ironThe specimens with different wall thickness of 4.5%carbon equivalent were poured into the sand mold,and the metallographic structure of the primary phase was observed.Then,the samples with different wall thickness were treated with different heating and cooling rates and times of rise and fall by DSC,and the cooling curves of the solidification process was obtained.(2)Study on the primary phase of aluminum alloyThe samples of Al-7%wt Si,Al-20%wt Si,Al-10%wt Cu and Al-20%wt Cu alloys with different wall thickness were poured in a vacuum melting furnace,and the metallographic structure of the primary phase(α-Al,primary silicon)was observed.By means of DSC,the samples with different wall thickness were treated with different heating and cooling conditions,and the cooling curves of the solidification process was obtained.(3)Calculation of solid-liquid interfacial energy of primary phase-liquid phase of vermicular graphite cast iron and aluminum alloyThe enthalpy during solidification of the primary phase was calculated by the DSC cooling curves,and the solid-liquid interfacial energy of the primary phase and liquid phase of the alloy was calculated by the Turnbull formula.It was found that for alloys with the same composition,different wall thickness and different rising and cooling rate have influence on the value of interfacial energy.(4)Influence of interfacial energy on dendrite morphology in microstructure simulationBy simulating different wall thickness castings of single crystal and polycrystal of Al-10wt Cu,founding that with the decrease of the interfacial energy,the secondary dendrite arm of primary phase α-Al developed gradually and the coarse dendrite forms at the low cooling rate.The simulation result is consistent with the experimental results and the accuracy of the variation law of interfacial energy obtained by calculation is verified.