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Environmental Strength Evaluation and Investigation into Degradation Mechanisms of Advanced Metallic Materials based upon Analyses of State of Hydrogen and Nanofractography

基于氢态和纳米断口分析的先进金属材料的环境强度评价和降解机制研究

基本信息

批准号：
11450043
负责人：
KOMAI Kenjiro
金额：
$ 9.54万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

Advanced metallic materials are sensitive to an environment and in order to clarify the degradation mechanisms and to improve the toughness of these metallic materials in a service environment, we must clarify the process of hydrogen entry as well as the hydrogen trap sites in the material. In this research project, thermal desorption spectroscopy of hydrogens is applied to analyze the state of hydrogen in the material, or hydrogen trap sites, and correlate the responsible hydrogen in the material to hydrogen embrittlement : the materials investigated are titanium aluminides intermetallic compound and Ti-6Al-4V alloys, and the influence of environment on fatigue crack growth behavior was investigated. In the case of titanium aluminides, the tensile strength of the duplex material decreases in order of a water molecule content in an environment : the strength in vacuum is the highest, and decreases in order of laboratory air and water. In the case of the lamellar material, the fatigue c … More rack growth rate in dry air is higher in the R-C crack plane orientation than that in L-C crack plane orientation : the crack growth rate becomes higher when the crack grows as the lamellae are tearing off. However, in the case of the duplex material, the crack growth rate in the R-C crack plane orientation is smaller in low ΔK (ΔK_<off>) region. When the cathodic charging is applied, the fatigue crack growth rate becomes higher than that in dry air, in particular at higher stress intensity factor range. The hydrogen evolution rate is increased by cathodic charging, with lower temperature peaks and higher ones. The peaks at lower temperatures are correlated with hydrides decomposition and detrapping of hydrogen from microstructural imperfections such as microvoids. As received materials also shows a evolution peak at a higher temperature, and the evolution rate is almost independent of cathodic charging. In addition, the evolution rate at a higher temperature above 800℃ is increased by cathodic charging. These hydrogens are considered to have an important role on fatigue crack growth acceleration. In contrast with these, the crack growth rate of Ti-6Al-4V alloy is sensitive to environment when the crack plane orientation is T-L, whereas the crack growth rate in a solution is almost equal to that conducted in dry air. However, the crack path changes towards the longitudinal direction, when the applied stress intensity factor range exceeds a certain value. The hydrogen evolution kinetics are independent of the testing environment, or the acceleration of crack growth, and the mechanisms of the crack acceleration are discussed. Less

先进金属材料对环境非常敏感，为了弄清材料在服役环境中的劣化机理和提高材料的韧性，必须弄清材料中氢进入的过程和氢陷阱的位置。本研究利用氢的热脱附谱分析材料中氢的状态，即氢陷阱位置，并将材料中的氢与氢脆联系起来：研究材料为钛铝金属间化合物和Ti-6Al-4V合金，研究环境对疲劳裂纹扩展行为的影响。在钛铝化物的情况下，双相材料的拉伸强度在环境中按照水分子含量的顺序降低：真空中的强度最高，并且按照实验室空气和水的顺序降低。在层状材料的情况下， ...更多信息在干燥空气中，R-C裂纹面取向的裂纹扩展速率大于L-C裂纹面取向的裂纹扩展速率：裂纹扩展速率随层板撕裂而增大。而对于双相材料，在低ΔK（Δ K_0）区，R-C裂纹面取向的裂纹扩展速率较小<off>。当施加阴极充电时，疲劳裂纹扩展速率变得比在干燥空气中更高，特别是在较高的应力强度因子范围内。阴极充电提高了析氢速率，具有较低的温度峰和较高的温度峰。在较低温度下的峰值与氢的分解和从微观结构缺陷如微孔中脱陷有关。接收态材料在较高温度下也有一个析出峰，析出速率几乎与阴极充电无关。此外，在800℃以上的较高温度下，阴极充电会增加析出速率。这些氢被认为对疲劳裂纹扩展加速有重要作用。与此相反，Ti-6Al-4V合金在T-L裂纹面取向下的裂纹扩展速率对环境敏感，而在溶液中的裂纹扩展速率与在干燥空气中的裂纹扩展速率几乎相等。当应力强度因子超过一定范围时，裂纹路径向纵向方向改变。氢的析出动力学与试验环境无关，也与裂纹的加速扩展无关，并讨论了裂纹加速扩展的机理。少