Liquid metals: structure and diffusion

熔化和铸造是将金属或合金熔化，然后倒入模具中，并允许其凝固形成特定固体形状的过程。自公元前4000年左右开始的铜时代以来，人类一直在使用熔化和铸造。最初，铸造仅限于小而简单的形状，如小雕像、烹饪锅、刀等。随着人类从青铜时代、铁器时代和工业革命到今天的进步，金属合金变得更加复杂，模具也越来越复杂。今天，由熔融金属制成的铸件几乎渗透到日常生活的方方面面，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，一直到铸造由非常复杂的高温合金制成的单晶涡轮叶片，用于飞机喷气发动机。 尽管液态金属在铸造过程中的使用历史悠久，但人们对它们的了解还不够深入。长期以来，人们一直认为液态金属由近乎随机的原子混合物组成，它们只具有短程有序，而不是固态的长程有序。然而，最近的数据表明，液态可能更复杂，不同的金属和合金可能会有很大的不同。此外，人们对液态金属中的原子迁移也知之甚少，凝固过程中液态金属中原子的迁移部分决定了凝固铸件的性能。要了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态结构，确定其中的扩散系数，并将这些系数与结构联系起来。除了增加液态金属和液态扩散的知识外，还将利用对这些主题的更多知识来进一步优化冶炼和铸造工艺，从而生产出更高质量、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.