Undercoolability of copper bulk samples
Undercoolability of copper bulk samples
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DOI：
10.1007/bf00720207
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发表时间：
1989-12
期刊：
影响因子：
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通讯作者：
M. Costa Agra Mello;C. S. Kiminami
中科院分区：
文献类型：
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作者：
M. Costa Agra Mello;C. S. Kiminami
在快速凝固过程中，如熔融纺丝和雾化，快速热提取的要求限制了最终产品的质量。然而，在块状过冷中，晶核被最小化或完全消除，因此不存在这种限制，并且有可能在不随后凝结条带、片状或粉末的情况下生产大块产品，同时保留快速凝固所获得的全部益处[1]。因此，研究过冷度是非常重要的。熔体中潜在的异质成核剂可能来自用于制备大块样品的材料中存在的杂质，也可能是各种熔体-金属-环境反应的结果，也可能在例如熔化阶段形成氧化物、硫化物、硫氧化物和碳化物。因此，过冷大块样品的最有效方法是通过悬浮或将熔融金属包裹在合适的玻璃或渣层中，将熔融金属从坩埚壁上隔离[2-4]。用后一种技术研究了铜块样品的过冷性，其结果如本文所示。铜块样品由99.999%纯度的铜丸制备而成，每个样品约1.2g。样品在稀释的王水中蚀刻，以减少表面不均一性[5，6]，并在干燥的石英坩埚(直径7 mm，高度48 mm)中加入约1.2g玻璃渣(商业硅酸盐玻璃，软化温度1073K)。熔化是在电阻炉中进行的，如图1所示。通过将热电偶放置在坩埚壁外，避免了热电偶尖端的异质形核。在使用两个热电偶的单独实验中，熔体-外部热电偶的温度不同-
In rapid solidification processing, such as melt-spinning and atomization, the requirement of rapid heat extraction limits the mass of the end-product. However, in bulk undercooling nucleants are minimized or completely eliminated, so that limitation does not exist and it is possible to produce a bulk product without subsequent consolidation of ribbons, flakes or powders, while retaining the full benefits achieved by rapid solidification [1]. For this reason undercooling studies are of utmost importance. Potentially heterogeneous nucleants in the melt may originate from impurities that are present in the materials used to prepare the bulk sample, or may be the result of various melt-metal-environment reactions and may also form as oxides, sulphides, oxysulphides and carbides, for example, during the melting stage. Thus, the most effective way of supercooling bulk samples consists of isolating the molten metal from the crucible walls either by levitation or by encasing it in a suitable glass or slag layer [2-4]. The latter technique was used to study the undercoolability of copper bulk samples, the results of which are presented in this letter.Copper bulk samples (about 1.2 g each) were prepared from 99.999% purity copper shot. Samples were etched in dilute aqua regia to reduce surface heterogenities [5, 6] and added to about 1.2 g glass slag (commercial silicate glass, softening temperature 1073 K) in a dry quartz crucible (7 mm id and 48 mm height). The melting took place in an electric resistance furnace, as shown in Fig. 1. Heterogeneous nucleation at the thermocouple tip was avoided by placing it just outside the crucible wall. In a separate experiment in which two thermocouples were used, the melt-external thermocouple temperature differ-