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以NH4Cl-70wt%H2O溶液为模型合金,考察了型壁冷却条件对液固相变形核及晶粒生长过程的影响。实验发现:在相同的充型温度下,降低型壁的温度,溶液过冷度增大,形核率增大,出现了“爆炸形核”现象;但当进一步降低型壁温度时,反而出现了形核率随过冷度变化趋势逆转的现象,分析其原因是原子扩散动力学,以及相变热力学耦合作用的结果,这与金属体系不同冷却速度条件下的形核过程呈现出同样的规律,说明NH4Cl-70wt%H2O溶液与金属体系在形核特性上具有相似性,可用于金属形核过程的良好模拟。
Taking NH4Cl-70wt% H2O solution as the model alloy, the effects of wall cooling conditions on liquid-solid phase deformation nuclei and grain growth were investigated. The experimental results show that under the same filling temperature, the temperature of the wall decreases, the undercooling of the solution increases, the nucleation rate increases, and the phenomenon of “explosion nucleation ” appears. However, when the wall temperature is further reduced, Instead, the phenomenon that the nucleation rate reverses with the variation trend of undercooling appears. The reason for the analysis is the result of the atom diffusion kinetics and the coupling effect of phase transition thermodynamics. The nucleation process under the different cooling rates of the metal system shows the same The results show that the NH4Cl-70wt% H2O solution is similar to the metal system in nucleation characteristics and can be used to simulate the metal nucleation process.