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首页> 外文期刊>ISIJ international >Semi-solid Processing of Alloys: Principles, Thermodynamic Selection Criteria, Applicability
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Semi-solid Processing of Alloys: Principles, Thermodynamic Selection Criteria, Applicability

机译：合金的半固态加工：原理，热力学选择标准，适用性

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Semi-solid processing (SSP) of alloys makes use of the thixotropic properties of two-phase mixtures of globulites and liquid. These materials whose viscosity decreases under shear deformation and increases again once the shear action ceases, can be handled almost like solids in the absence of shear stress and they can flow like viscous liquids when deformation forces are applied. SSP requires a wide melting interval of the alloy, a low temperature sensitivity of the phase fractions in the slurry and a tendency to form a finegrained globulitic microstructure. The numeric simulation of solidification has proven useful for the selection of alloys to be processed in the semi-solid state. To obtain results applicable in practice, the methods to be used depend on the alloy systems, reaching from equilibrium calculations and Scheil-Gulliver estimations to diffusion simulations. All simulations depend on reliable thermodynamic and kinetic databases. Iristead of using only the slope of the fraction liquid curve at 50 percent liquid as selection criterion, we suggest to use the thixo ranges DELTA T~(40-60) for thixocasting and DELTA T~(40-60) for thixoforging. Using these selection criteria we investigated the suitability of three Al alloys and three steels including the influence of compositional variations. So far, the industrial large-scale production of parts by SSP has been confined to aluminium alloys, although extensive development efforts are being made to apply the process to magnesium, to nickel alloys and to steels.
机译：合金的半固态加工（SSP）利用了球石和液体两相混合物的触变性。这些材料的粘度在剪切变形下会降低，一旦剪切作用停止，粘度会再次增加，可以在没有剪切应力的情况下像固体一样处理，在施加变形力时它们可以像粘性液体一样流动。 SSP需要较宽的合金熔化间隔，对浆液中的相分数具有较低的温度敏感性，并且倾向于形成细粒的球状微结构。凝固的数值模拟已被证明对选择半固态待加工合金很有用。为了获得可用于实践的结果，所使用的方法取决于合金系统，从平衡计算和Scheil-Gulliver估计到扩散模拟。所有模拟都依赖于可靠的热力学和动力学数据库。代替仅使用馏分液体曲线在50％液体时的斜率作为选择标准，我们建议使用触变范围DELTA T〜（40-60）进行触变铸造，使用DELTA T〜（40-60）进行触变铸造。使用这些选择标准，我们研究了三种铝合金和三种钢的适用性，包括成分变化的影响。迄今为止，尽管为将这种工艺应用于镁，镍合金和钢已进行了广泛的开发努力，但通过SSP进行的工业大规模零件生产仍局限于铝合金。

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