初级金属固溶体的固相线

本文提出二元合金A_(1-x)B_x的初级金属固溶体的固相线的计算公式为:T_m(x)=T_(mA)F(x),其中T_(mA)是A金属的熔点,F(x)是以X为变量、包含A和B的原子密度N、价数Z、熔化体积增率(△V/V)和熔化熵△S的解析函数.对于以Cu、Ag、Au为基的、包含一价到四价的简单金属的24种初级金属固溶体的固相线作了理论计算.与实验结果符合较好.对于三元合金也作了相应的推广.     

凝固模拟热物性参数数据库系统的研究与开发

针对凝固模拟中热物性参数数据量大、种类多,数据查找困难、更新不便的问题,研究开发了一套热物性参数数据库系统.系统包括参数录入、数据更新、数据查询和液固相线温度计算模块,实现了对参数数据的集中有效管理.     

半固态固相体积分数的拟合公式

提出了先用抛物线拟合合金液相线和固相线、再用杠杆定律求合金半固态固相体积分数公式的新方法.用新方法求得的Mg-Pb合金半固态固相体积分数公式不仅计算精度高,如Mg-40%Pb合金半固态固相体积分数公式的计算值与测量值的最大绝对误差仅为0.022,而且,因为半固态固相体积分数公式中包含温度和合金元素含量两个自变量,所以扩大了半固态固相体积分数公式的应用范围.     

A System of Process Models for Estimating Parameters of Continuous Casting Using Near Solidus Properties of Steel

The quality of a continuously cast product depends on the process condition, which, in turn, depends on process parameters. To be able to set the correct parameter values, it is important that behavior of the steel being cast under different casting conditions is well understood. This will need the knowledge of the mechanical behavior of steels at temperatures near the solidus. This paper presents, in detail, how these properties were modeled as a function of steel grade, temperature, and stresses that arise during casting. These models have been used to develop an integrated system that is capable of simulating various process conditions that may be encountered during continuous casting. The details of how these models were developed, verified, and used to develop the integrated system are presented in this paper.     

Ag-Cu-Si合金的熔化特性

用ＤＴＡ 法测定Ａｇ － Ｃｕ － Ｓｉ 合金中（ＣｕＡｇｘ）１００ － ｙ － Ｓｉｙ（ｘ ＝ １０ ， ２０ ， ３０ ， ４０ ， ５０ ，７２） 及（ＣｕＳｉ５） － Ａｇ ７ 个特定成份伪二元系的固相线、液相线。结果表明， Ｓｉ 含量对Ａｇ － Ｃｕ合金液相线温度及熔化间隔Δｔ 的影响是显著的。在研究的Ｓｉ 名誉含量０ ～１０ｗｔ％ ， 其液相线呈“Ｖ”型变化。Δｔ 值小对于钎料合金选择和降低Ａｇ 含量是有利的     

Solidification structure of CaO–SiO2–MgO–Al2O3 (–CaF2) systems and computational phase equilibria: Crystallization of MgAl2O4 spinel

The solidification behaviour of the CaO–SiO₂–Al₂O₃–CaF₂–10% MgO system, which is similar to the inclusion compositions in the stainless steel and the crystallization of spinel have been investigated using XRD, SEM-EDS, and an image analyser. The solidification mode and the phase equilibria were computed by employing thermochemical software. The liquidus temperature of the oxides containing 5% CaF₂ increases with increasing alumina content from 10% to 30%, while the solidus temperature has little dependence on alumina content. The size of spinel crystals in the final microstructure increases on increasing the content of alumina, resulting from that the oxides spending more time at higher temperatures below the liquidus temperature, where crystal growth is generally faster than nucleation, during slow cooling. The liquidus temperature of the oxides containing 30% Al₂O₃ is scarcely varied, while the solidus temperature decreases by increasing the content of CaF₂ to 10%. The size of spinel crystals decreases as the content of CaF₂ increases, resulting from the fact that the oxides could spend more time at relatively lower temperatures, where nucleation is faster than growth, during the cooling process.     

电磁场对7075铝合金液固相线温度的影响

分别使7075铝合金在磁场强度为0．06T的直流磁场或交流磁场作用下凝固,通过在凝固过程中测定电阻-温度曲线,确定了合金在不同条件下凝固的液相线和固相线温度。试验结果表明：合金在直流磁场中凝固,液、固相线温度均明显降低,液相线温度由未加磁场试样的630℃降低到627．5℃,固相线温度由未加磁场时的520℃降低到510℃,同时结晶温度间隔变大;而在交流磁场中凝固的试样,其液相线和固相线温度均明显提高,液相线温度比没有磁场时升高了7．5℃,固相线温度升高了10℃,并且结晶温度间隔变小。     

碳钢实际固相线温度的理论预测及回归分析

基于多元合金两相区凝固计算仿真软件MAMSV1.0,针对多种溶质成分组成的碳钢,在通常的连铸板坯冷却条件下对其实际固相线温度进行了仿真计算,并根据理论预测结果按最小二乘法进行了回归分析,获得了碳钢实际固相线温度与主要溶质成分质量浓度之间的近似关系式,该回归计算式可以方便快捷地在板坯连铸浇注过程实时跟踪控制模型中加以耦合应用。     

Microstructural Evolution of Solid-solution-treated Zn-22Al in the Semisolid State

The effect of solid-solution-treatment on the semisolid microstructure of Zn—22AI with developed dendrites was investigated.Forming Zn—22AI products by semisolid metal processing offers significant advantages,such as reductions in macro-segregation,porosity and forming costs.Thermal and microstructural analyses of the formed Zn—22AI alloy were performed by differential scanning calorimetry,scanning electron microscopy and optical microscopy.The changes in the microstructures and phase transformation in response to various solid-solution -treatments were analysed.In this study,as-cast samples were held isothermally at 330℃for 0.5—5 h and then partially remelted at a semisolid temperature of 438℃for 1 h to produce a solid-globular grain structure in a liquid matrix.A non-dendritic semisolid microstructure could not be obtained when the traditionally cast Zn—22AI alloy with developed dendrites was subjected directly to partial remelting.After solid-solution-treatment at 330℃,the black interdendritic eutectics were dissolved,and the dendritic structures gradually transformed into uniformβstructures when the treatment time was increased.The coarsened and merged dendrites were separated as a result of penetration by the liquid phase and melting of the residual eutectic at sites along the former grain boundaries.The microstructure of the solid-solution-treated sample transformed into a small globular structure;the best shape factor of 0.9,corresponding to a particle size of 40±16μm,is achieved when the sample was treated for 3 h followed by direct partial remelting into its semisolid zone.     

Experimental and simulation studies on thixoforming of AA 2017 alloy

Thixoforming is one of the near net shaped manufacturing processes which in the product will be formed between the solidus and the liquidus temperatures of the alloy. In the present work, a finite element based simulation study has been performed to simulate the thixoextrusion of AA 2017 alloy in the semisolid range. The alloy has been heated between 570 and 610°C and it was extruded in a die having die cone angles of 30, 45 and 60°. Simulation studies have been performed by using the constitutive relation that was developed by performing disc compression tests at different temperatures and strain rates. A good agreement was found between the experimental and the simulation results.