Powdering limit of hydrogen absorbing intermetallic compounds

吸氢金属间化合物粉化极限

基本信息

批准号：
12305046
负责人：
YAMAGUCHI Masaharu
金额：
$ 26.14万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

Mechanisms of the reversible hydrogen absorption and desorption in Ti_3Al-base alloys was studied by means of pressure-composition isotherm measurements and microscopy observations before and after hydrogen absorption on specimens subject to heat treatment and cold rolling. The alpha-hydride to beta-hydride phase transformation in the Ti_3Al-base alloys occurs at a very low pressure and is reversible under normal conditions. However, the transformation between beta and gamma hydrides can be made reversible if the specimen is heat treated so that it contains O-phase in its microstructure or is appropriately deformed by cold rolling. The beneficial effects of O-phase on hydrogen absorption/desorption were demonstrated in three Ti-AT-Nb alloys with compositions in the vicinity of Ti_2NbAl. The beneficial effects are found to be related to the structure and strain field of O-phase rather than the interface between the O-phase and matrix. Their hydrogen absorption and desorption properties are improved when they are mildly deformed. Microstructure observations show that the beta and gamma hydride transformation occurs in a way very similar to the martensitic transformation and can be analyzed within the frame work of the martensitic transformation. The lattice shear deformation is accomplished by a high density of screw dislocations in the transformed laths. Such screw dislocations can be introduced by cold rolling.The hydrogen absorption/desorption properties of other intermetallic materials may be expected to be improved similarly to Ti_3Al-base alloys. Thus, the hydrogen absorption and desorption of Mg-Ca-Ni alloys, which absorb hydrogen easily and form a very stable hydride, was investigated. However, we have not succeeded in enhancing their hydrogen absorption and desorption properties yet. Further work is needed to clarify the reason for this.

通过对热处理和冷轧试样吸氢前后的压力-成分等温线测量和显微观察，研究了Ti_3Al基合金中可逆吸放氢的机理。 Ti_3Al基合金中的α-氢化物到β-氢化物相变发生在非常低的压力下，并且在正常条件下是可逆的。然而，如果对试样进行热处理使其显微结构中含有O相或通过冷轧进行适当变形，则β氢化物和γ氢化物之间的转变可以是可逆的。 O 相对氢吸收/解吸的有益影响在三种成分接近 Ti_2NbAl 的 Ti-AT-Nb 合金中得到了证明。研究发现，有益效果与O相的结构和应变场有关，而不是与O相和基体之间的界面有关。当它们轻微变形时，它们的吸氢和解吸性能得到改善。微观结构观察表明，β和γ氢化物转变的发生方式与马氏体转变非常相似，并且可以在马氏体转变的框架内进行分析。晶格剪切变形是通过变形板条中高密度的螺旋位错来实现的。这种螺旋位错可以通过冷轧引入。其他金属间材料的吸/放氢性能有望得到与Ti_3Al基合金类似的改善。因此，研究了容易吸收氢并形成非常稳定的氢化物的Mg-Ca-Ni合金的氢吸收和解吸。然而，我们尚未成功提高其氢吸收和解吸性能。需要进一步的工作来澄清其原因。