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The Effect of Crystal Structure and Microstructure on the Hydrogen-Induced Embrittlement of Intermetallic Compounds

晶体结构和微观结构对金属间化合物氢致脆化的影响

基本信息

批准号：
10650684
负责人：
TAKASUGI Takayuki
金额：
$ 2.24万
依托单位：
Osaka Prefecture University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

Using Ni_3(Si, Ti), and Co_3Ti intermetallic compounds with L1_2-type structure, the influence of atomic composition at grain boundaries, grain size and the second-phase dispersions has been observed in this study. The following results were obtained.1) The atomic compositions at the grain boundaries of Ni_3(Si, Ti) alloy were analyzed by means of Auger spectroscopy, and then correlated with the tensile ductility in air. Consequently, it was found that grain boundary compositions such as boron as well as constituent atoms strongly affected the tensile ductility of Ni_3(Si, Ti) alloy deformed in air. It was suggested that boron atoms enriched at the grain boundaries affect decomposition process of moisture in air, or block the migration and the condensation of hydrogen, reducing the environmental embrittlement.2) It was found that the Nb containing second-phase dispersions suppress the moisture-induced embrittlement of Ni_3(Si, Ti) alloys though those enhance the strength of Ni_3(Si, Ti) alloys. This result was interpreted so that the absorbed hydrogen can be trapped within the second-phase dispersions or at interface between the second-phase dispersions and the matrix, or in the plastically deformed regions adjoining the second-phase dispersions. Based on these results, high-temperature structural material with high fracture toughness at low temperature and also high flow strength at high temperature was developed.3) It was found that fine-grained microstructure was effective in reducing the moisture-induced embrittlement of Co_3Ti alloy. Also, the moisture-induced embrittlement of Co_3Ti alloy was reduced in the low deformation rate region. As a corresponding mechanism, oxidation and related oxide product formed at free surface of Co_3Ti alloy reduce the decomposition of moisture in air, resulting in the moisture-induced embrittlement.

本文以L1_2型结构的Ni_3（Si，Ti）和Co_3Ti金属间化合物为研究对象，观察了晶界原子组成、晶粒尺寸和第二相弥散度的影响。1）利用俄歇能谱分析了Ni_3（Si，Ti）合金的晶界原子组成，并与其在空气中的拉伸塑性进行了关联。结果表明，晶界成分（如硼）和晶界原子对Ni_3（Si，Ti）合金在空气中变形后的拉伸塑性有很大影响。结果表明，晶界上富集的硼原子影响了水分在空气中的分解过程，或阻碍了氢的迁移和凝聚，从而降低了环境脆化。2）含Nb的第二相弥散相虽然提高了Ni_3（Si，Ti）合金的强度，但抑制了Ni_3（Si，Ti）合金的湿致脆化。这一结果被解释为吸收的氢可以被捕获在第二相分散体内或在第二相分散体和基体之间的界面处，或在邻接第二相分散体的塑性变形区域中。在此基础上，开发出了低温下具有高断裂韧性，高温下具有高流动强度的高温结构材料。3）研究发现，细晶组织能有效地降低Co_3Ti合金的湿致脆化。在低变形速率区，Co_3Ti合金的湿脆化程度降低。作为相应的机制，Co_3Ti合金自由表面的氧化及相应的氧化物产物减少了水分在空气中的分解，导致了湿脆。