Construction of Database of Alloys for the prediction of Casting Structure

为了建立铸件组织预测所需的合金数据库，研究了铸件组织预测所需的项目和方法。对铝合金的非均相形核参数进行了评价。1)非均相成核频率分布评价为了选择数据库的成核模型，将纯Al、Al- cu、Al- si、Al- fe、Al- ti等合金样品在K_2SO_4-Li_2SO_4熔盐中搅拌熔化分散，将分散的合金颗粒在K_2SO_4-Li_2SO_4熔盐中重新熔化并测量其熔点。结果表明，各颗粒的形核频率随过冷度的增加而增加，但在过冷度最高时有所降低。结果表明，在常规铸造条件下，非均质形核采用过冷的简单幂型表示。在本研究中，通过对比实验得到的合金形核结构和模拟得到的合金形核结构来评价合金的形核参数。为了对多组分合金的组织形成进行模拟，需要进行精确的传热计算，以产生与实验得到的铸件相同的温度场。为了模拟多组分合金凝固过程中的传热过程，采用热力学计算方法，建立了一种基于焓法的新方法。3)铝合金成核参数评价对铝基二元合金和工业合金进行了定向凝固实验。采用蒙特卡罗方法模拟了柱状向等轴转变（CET）的实验观测位置，并通过生成每个样品的CET位置来确定成核参数。无论是二元合金还是商用铝基合金，其成核参数都随着硅含量的增加而增加。期望利用上述参数可以预测更大型或更复杂铸件的组织，并可通过实验室规模试验进行评价。少

In order to construct the database of alloys for the prediction of casting structure, Items and methods that are required for the construction were investigated. The heterogeneous nucleation parameters for aluminum base alloys were evaluated.1) Evaluation of heterogeneous nucleation frequency distributionIn order to select the nucleation model for the database, sample alloys such as pure Al, Al-Cu, Al-Si, Al-Fe, Al-Ti were melted and dispersed by stirring in K_2S0_4-Li_2SO_4 molten salt Each dispersed particle of alloys was re-melted and its melting point was measured in the K_2SO_4-Li_2SO_4 molten salt. As the result, the nucleation frequency of each particle increased with increasing undercooling, but decreased at the highest undercooling. It was confirmed that a simple power form with respect to undercooling for the expression of heterogeneous nucleation was adopted for conventional casting condition.2) Heat transfer analysis for a multi-component alloy by using thermodynamic calcul … More ationIn the present study, the nucleation parameters of alloys were evaluated by comparing experimentally obtained structures and simulated ones. In order to carry out the simulation for the structure formation of a multi-component alloy, precise heat transfer calculation is needed to produce the same temperature field with the casting obtained by the experiment. In order to simulate the heat transfer process during the solidification of a multi-component alloy, a new method was developed based on the enthalpy method by using a thermodynamic calculation.3) Evaluation of nucleation parameter for aluminum alloysUnidirectional solidification experiment of aluminum base binary and commercial alloys were carried out. Experimentally observed locations of columnar to equiaxed transition (CET) were simulated by a method based on the Monte Carlo procedure, and nucleation parameters were determined by producing the locations of CET for each sample. The nucleation parameters, which are expressed as a power with respect to undercooling, increased with increasing silicon content for both binary and commercial aluminum base alloys.It is expected that the structure of more large or complicated casting can be predicted by using above parameters which can be evaluated by a laboratory scale experiment. Less