Macro-and Micro-solidification Simulation By Transparent Organic Alloys

Solidification interface morphology depends on the liquid-solid interface characteristic and solidification driving force. The liquid-solid interface characteristic determines the responses of interface morphology to solidification driving force. In general, the similar liquid-solid interface characteristic will exhibit similar kinetic and interface morphological behavior. Succinonitrile(SCN) is a kind of transparent organic alloys with body-centered cubic structure which has a similar interface characteristic with metals, it was widely used in the solidification theoretic researches since it's thermodynamic data is complete and has a similar solidification interface behaviors with metals. Lots of the important progress in solidification principle accept by the academia is firstly dependent on the SCN experimental results, and then further verified in many ways including the experiments of the metal alloys.In this paper, high purity SCN was prepared high efficiently through a modified purification equipment, which was used to carry out the researches on macro- and micro-solidification simulation. For micro-solidification researches, the stability parameter for the dendritic growth was investigated by the experiment of free dendritic growth from supercooling melt;For macro-one, the evolution process and formation mechanism of precipitating gas hole was studied by in situ observation of the evolution of precipitating gas hole during casting. The main conclusions are obtained as follows:1. The purification effect of SCN was investigated by the comparison between rectification under vacuum and vacuum distillation adding zone refining, and it is found that, rectification under vacuum have higher purification efficiency for SCN, and SCN with the purify above 99.99% was prepared.2. The water bath, with the temperature control within ±0.004°C, was designed and fabricated, and further calibrated based on the triple point of water. Meantime, the growth and observation equipment for free dendrite was also make.3. The researches on the dendritic growth dynamic from the supercooling melt were carried out through the free dendritic experiments of the high-purity succinonitrile. It is found that the stability parameter for dendritic growth is close to the value predicted by MSC microscopic solvability theory and LM-K marginalstability hypothesis and there is a big difference between the experimental results and that by GIW global interfacial wave theory.4. In situ observation of the evolution of precipitating gas hole in casting was performed by used the transparent organic alloys. In pure substance solidification, precipitating gas hole arise after the shell appeared, develop from wall to center with solidification, present the growth of gas strip. In alloy solidification, precipitating gas hole arise in solidification anaphase with the heat check and shrinkage porosity beginning formation, present a certain extent gather. Precipitating gas hole will become denser if increasing the superheat of fused mass before casting, and the number and range of precipitating gas hole will be reduced if reducing the temperature of cast and ambient. The flaw of precipitating gas hole, heat check and shrinkage porosity can be effectively checked buy vacuum degassing.