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Measurement of Intrinsic Mechanical Properties of Brittle Metallic Materials with Ideally Clean Surface and Approach to Environmental Brittlement

具有理想清洁表面的脆性金属材料的固有机械性能的测量和环境脆化的方法

基本信息

批准号：
07455279
负责人：
MORINAGA Masahiko
金额：
$ 4.93万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07455279/
关键词：
Metallic materials Molecular orbital method Mechanical properties Surface 分子軌道計算

项目摘要

Recently, it has been revealed that mechanical properties of metallic materials are strongly dependent on the surface conditions of specimens and on the test environments as well. The purposes of this research are to get intrinsic mechanical properties of metals and alloys and also to get information of environmental brittlement. For these purposes a new tensile test machine was made. It was equipped with an ultra-high vacuum chamber and an Ar ion gun to clean the specimen surface by etching. With this machine, tensile tests were carried out by controlling the specimen surface-state and the test atmosphere in an ideal manner as much as possible.Materials used in this study were five pure metals, Cr, Mo, Ti, Ni, Al, and two alloys, Ti-6%Al-4%V and Fe-3%Si. Except for T-6%Al-4%V,all the specimens were single crystals. A series of experiments was carried out using the specimens with and without surface etching. In addition, the DV-Xalpha molecular orbital calculation was performed to simulate the electronic states of impurity elements, H,O,N,C and B in Cr.The results obtained in this study were summarized as follows ;(1) The existence of oxide films such as NiO on Ni, Al_2O_3 on Al and Fe_2O_3 on Fe-3%Si, was identified by the X-ray photoelectron spectroscopy. The yield stress and tensile stress of bulk metals and alloys were sensitive to the existence of such thin oxide or oxide-like films on the surface. Both the intrinsic yield and tensile stresses of most metals and alloys were supposed to be higher than the reported values which have been obtained by a conventional mechanical test in air using the specimens coated with some oxide films.(2) It was found from the calculation that impurity elements such as B and C tended to make the strong covalent bond with Cr and to affect the mechanical properties of Cr metal.

近年来研究表明，金属材料的力学性能与试样的表面状态和试验环境有很大的关系。本研究的目的是获得金属和合金的本征力学性能，同时也获得环境脆性信息。为此，制造了一种新的拉伸试验机。它配备了一个超高真空室和一个Ar离子枪，通过蚀刻清洁样品表面。采用Cr、Mo、Ti、Ni、Al五种纯金属和Ti-6%Al-4%V、Fe-3%Si两种合金，通过尽可能理想地控制试样表面状态和试验气氛，进行拉伸试验。除T-6%Al-4%V外，其余试样均为单晶。使用表面蚀刻和未蚀刻的试样进行了一系列实验。另外，还利用DV-X α分子轨道方法模拟了Cr中杂质元素H、O、N、C和B的电子态，得到了如下结果：（1）X射线光电子能谱证实了Ni表面NiO、Al表面Al_2O_3和Fe-3%Si表面Fe_2O_3等氧化膜的存在。大块金属和合金的屈服应力和拉伸应力对表面上这种薄的氧化物或类氧化物膜的存在敏感。大多数金属和合金的本征屈服应力和拉应力都高于用氧化膜试样在空气中进行常规力学试验所得到的值。(2)计算结果表明，杂质元素B、C等易与Cr形成较强的共价键，影响Cr金属的力学性能。