Construction of Database of Alloys for the prediction of Casting Structure

为了建立用于铸件组织预测的合金数据库，研究了建立合金数据库所需的项目和方法。1）非均匀形核频率分布的评价为了选择数据库的形核模型，对纯Al、Al-Cu、Al-Si、Al-Fe、在K_2SO_4-Li_2SO_4熔盐中，通过搅拌使Al-Ti合金熔化并分散，合金中的每个分散粒子都被重新分散，在K_2SO_4-Li_2SO_4熔盐中熔融，测定了其熔点。结果表明，每个颗粒的形核频率随过冷度的增加而增加，但在最高过冷度时却降低。2）采用热力学计算方法对多元合金进行了传热分析，并对多元合金的非均匀形核过程进行了热力学计算，得到了非均匀形核过程的热力学方程。 ...更多信息 在本研究中，通过比较实验获得的结构和模拟的合金的形核参数进行评估。为了对多元合金的组织形成进行模拟，需要进行精确的传热计算，以产生与实验所得铸件相同的温度场。为了模拟多元合金凝固过程中的传热过程，采用热力学计算，在焓法的基础上发展了一种新的方法。3）铝合金形核参数的评价进行了铝基二元合金和商业合金的单向凝固实验。实验观察到的柱状晶等轴转变（CET）的位置进行了模拟的方法的基础上的Monte Carlo程序，和形核参数确定通过生产的CET为每个样品的位置。对于二元和工业铝基合金，形核参数（以过冷度的幂表示）随硅含量的增加而增加，可以用实验室规模的实验来评价，并可以用这些参数来预测更大或更复杂的铸件的组织。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