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Glassy embrittlement of chromium metal and its improved ductility by alloying elements

铬金属的玻璃脆化及其通过合金元素改善的延展性

基本信息

批准号：
05650671
负责人：
MORINAGA Masahiko
金额：
$ 1.41万
依托单位：
Toyohashi University of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

Chromium and its alloys are ones of the promising high temperature materials since they exhibit the excellent combination of low density, high creep strength and good oxidation resistence at high temperatures. However, there is still a large barrier to the practical use because of the poor ductility at room temperature. The purposes of this study are two-fold. One is to elucidate the mechanism for the embrittlement of chromium experimentally using a bend test and a small punch test. The other is to investigate a method for improving the ductility by the addition of alloying elements into chromium.As the result, it was found that plasticity of high-purity polycrystalline chromium was dependent largely on surface imperfections. The existence of small cracks on the surface induced it to be very brittle. Also, large environmental effects were observed on the ductility chromium. For example, the moisture existing in the test environment increased the ductility of pure chromium, which is in contrast to the observations in other metallic materials such as intermetallic compounds (e. g., FeAl TiAl) . In addition, it was shown for the first time that pure chromium exhinbited hydrogen embrittlement. All these phenomena observed in pure chromium were also found in Chromium alloys. Furthermore, the vanadium addition was shown to be most effective in improving the ductility of chromium among a variety of alloying elements including 3d, 4d and 5d transition metals. Thus, the present results provided us important information on the method for improving the ductility of chromium.

铬及其合金具有密度低、蠕变强度高、高温抗氧化性好等优点，是一种很有发展前途的高温材料。然而，由于其在室温下的延性较差，其实际应用仍有很大的障碍。这项研究的目的有两个。一种是通过弯曲试验和小冲孔试验来阐明铬的脆化机理。另一种是通过在铬中添加合金元素来改善塑性的方法。结果发现，高纯多晶铬的塑性在很大程度上取决于表面缺陷。表面小裂缝的存在使它变得非常易碎。此外，还观察到了环境对塑性铬的影响。例如，试验环境中存在的水分增加了纯铬的延展性，这与在其他金属材料中观察到的情况相反，如金属间化合物(如FeAl-TiAl)。此外，首次发现纯铬对氢脆有一定的抑制作用。在纯铬中观察到的所有这些现象也在铬合金中发现。此外，在包括3d、4d和5d过渡金属在内的各种合金元素中，添加钒对改善铬的延展性是最有效的。因此，本研究结果为改善铬的延展性提供了重要的信息。