Liquid metals: structure and diffusion

熔化和铸造，即金属或合金熔化然后倒入模具中并使其固化以形成特定固体形状的工艺，自公元前4000年开始的铜时代以来一直被人类使用。最初，铸件仅限于小型，简单的形状，如雕像，烹饪锅，刀等，随着人类通过青铜时代和铁器时代以及工业革命发展到今天，金属合金变得更加复杂，并且使用越来越复杂的模具。今天，由熔融金属制成的铸件几乎渗透到日常生活的各个方面，从简单的物体如铸铁煎锅和儿童玩具到更大更复杂的形状如汽车发动机缸体，一直到由非常复杂的高温合金制成并用于飞机喷气发动机的单晶涡轮机叶片。 尽管液态金属在铸造工艺中的应用历史悠久，但人们对液态金属的了解并不多。长期以来，人们一直认为液态金属是一种近似随机的原子混合物，与固态金属的长程有序相反，它只具有短程有序。然而，最近的数据表明，液态可能更加复杂，并且对于不同的金属和合金可能有很大不同。此外，液态金属中的原子输运也知之甚少，并且在凝固期间液态金属中的原子输运部分地决定了凝固铸件的性质。为了理解液态金属中原子输运的本质，需要一个液态结构的模型。 拟议的研究将检查选定的金属合金的液体结构，确定其中的扩散系数，并将系数与结构联系起来。除了增加液态金属和液体扩散的知识外，这些主题的知识将用于进一步优化熔炼和铸造工艺，从而获得更高质量，更具成本效益的铸件。

Melting and casting, processes whereby metals or alloys are melted then poured into molds and allowed to solidify to form a particular solid shape, have been used by humankind since the copper age which began about 4000 BCE. Initially, castings were limited to small, simple shapes such as figurines, cooking pots, knives, etc. As humankind progressed through the bronze age and iron age and the industrial revolution to the present day, the metal alloys became more sophisticated and increasingly complex molds were utilized. Today, castings made from molten metals pervade almost all aspects of everyday life, from simple objects such as cast iron frying pans and children's toys to larger and more complex shapes such as automobile engine blocks all the way to cast, single crystal turbine blades made from very sophisticated high temperature alloys and used in airplane jet engines. Despite their long history for use in casting processes, liquid metals are not well understood. It has long been considered that liquid metals comprise a near-random mixture of atoms possessing only short range order in contrast to the long range order of the solid state. However, more recent data suggest that the liquid state may be more complicated and may be considerably different for different metals and alloys. Further, atomic transport in liquid metals is also little understood and the transport of atoms in the liquid metal during solidification determines, in part, the properties of the solidified casting. To understand the nature of atomic transport in liquid metals requires a model for the liquid structure. The proposed research will examine the liquid structure of selected metal alloys, determine the diffusion coefficients therein and relate the coefficients to the structure. Besides adding to the knowledge of liquid metals and liquid diffusion, increased knowledge of these topics will be used to further optimize the smelting and casting processes resulting in higher quality, more cost-effective castings.