采用温度回升法对任意结晶区间的铸件凝固结晶潜热的数值计算

铸件凝固结晶潜热的释放行为与凝固传热、溶质传输及铸造合金种类与成分等诸多因素有关，合金凝固过程中其温度、固相体积分数与液相成分(T-fs—CL)三者之间一般存在着非线性强耦合关系．采用合金凝固传输统一模型及温度回升(补偿)法提出的处理任意结晶温度区间(包括零结晶区间)凝固潜热释放问题的数值迭代计算方法，对不同合金成分与不同固相反扩散效应的二维Al—Cu合金铸件定向凝固传输过程进行了数值计算，表明该方法对于从纯金属到共晶成分的不同成分合金及从Scheil模型到Lever-Rule模型之间的任意凝固模式均是有效的．将该方法推广应用于叶片铸件三维凝固传输过程的T-fs—CL耦合数值模拟仍显示出高的计算效率．通过对计算结果进行的三维图像数据处理，展示了铸件几何形状对凝固传输行为的重要影响．

NUMERICAL CALCULATION FOR LATENT HEAT RELEASES IN ALLOY CASTINGS OF ANY SOLIDIFICATION RANGE USING AN EXTENDED TEMPERATURE-COMPENSATION METHOD

Latent heat release relates to several factors, such as heat and solute mass transfers in the solidification process, in which strong nonlinear couplings among the temperature, solid fraction and liquid concentration (T-fs-CL) inherently exist. A previously proposed numerical iteration method, based on the continuum model of solidification transport phenomena (STP) and temperature compensation method, is used to further investigate the latent heat release problems in alloy solidifica-tions of any temperature range, including the case at a fixed solidification temperature. The method is applied to the STP-based numerical simulations for 2D Al-Cu blade-like castings of different nominal compositions and different solid back-diffusion effects. The validity and efficiency of the present method are demonstrated by the sample computations of several typical solidification cases from Scheil-type continuously to Lever-Rule model and of nine nominal compositions from almost zero to nearly the alloy's eutectic composition. The numerical method is confirmed by the 3D STP-based simulations for the directional solidification processes of real blade castings. The computation results show both the efficiency of the numerical iteration method and the remarkable influences of the casting shape on the solidification transport processes.