Liquid metals - diffusion and solidification

液态金属和合金中原子的运动，被称为液体扩散，是发生在铸造、焊接以及所有涉及熔化和凝固的过程中的重要传递过程。液体扩散在一定程度上决定了合金元素的分布，以及从熔融状态凝固的任何部件的微观组织和宏观组织，这反过来又有助于铸件和焊接部件的强度和韧性。尽管液体扩散很重要，但由于缺乏准确、可靠的数据，人们对构成扩散过程的原子运动知之甚少。直到最近，对流流掩盖了仅由扩散引起的原子运动。在微重力环境下进行的实验很少获得不受对流输送影响的准确结果，但微重力环境的费用和可及性限制了所能获得的信息量。最近的研究表明，在一定条件下，在单位重力下可以得到精确的液体扩散结果，并建议利用这些条件来获得大范围变量的数据，从而为液体扩散理论的发展提供一个数据库。

The motion of atoms in liquid metals and alloys, known as liquid diffusion, is an important transport process that occurs in castings, welds, and all processes that involve melting and solidification. Liquid diffusion determines, in part, the distribution of alloying elements, the microstructure and macrostructure of any component that was solidified from a molten condition which in turn contribute to the strength and toughness of castings and welded components. Despite the importance of liquid diffusion, little is known concerning the atomic motions that comprise the diffusion process because of the paucity of accurate, reliable data. Until recently, convective currents have masking the atomic motion due to diffusion alone. A very few accurate results free from convective transport have been obtained from experiments performed in microgravity but the expense of and accessibility to the microgravity environment limits the amount of information that can be obtained. It has recently been shown that accurate liquid diffusion results can be obtained in unit gravity under certain conditions and it is proposed that these conditions be utilized to obtain data for a wide range of variables thus providing a data base from which a theory for liquid diffusion may be developed.