应力状态和渗氢条件在非晶态NiCrFeSiB合金氢脆断裂中的作用

通过慢应变速率拉伸、断口观察和断裂力学分析等方法研究了非晶态NiCrFeSiB合金氢脆断裂过程和断口形态的关系.试样的应力状态,氢的渗入量及其在试样中的分布,以及非晶态合金塑性变形局部化的程度等因素对断裂过程都有影响.当渗氢量较低时,断裂方式主要由试样的应力状态所决定,发生近表面区的平面应力断裂和内部的平面应变断裂.当渗氢量较高,且氢由表面向内部分布的浓度梯度较陡时,发生表面区的"解理"型断裂和核心区的延性断裂.在渗氢量适中,氢浓度梯度平缓的条件下,出现由表面向内部塑性变形程度逐渐增大的"河流"形态.根据

THE EFFECTS OF STRESS STATE AND HYDROGEN PERMEATION ON HE FRACTURE OF AMORPHOUS NiCrFeSiB ALLOY

Hydrogen embrittlement fracture of amorphous NiCrFeSiB alloy has been investigated by constant extension rate testing after electrochemical charging. Under weak hydrogen charging condition, fracture was controlled mainly by stress state of the sample. If hydrogen permeation was strengthened, a hydrogen concentration gradient was set up and a "river" pattern on the fracture surface was observed which indicates the gradually increased plastic deformation from the surface to the inner of the sample before fracture. Under strong hydrogen charging condition,hydrogen content near the surface was high and its concentration gradient was very steep, leading to "cleavage" fracture near the surfaces and "ductile" fracture in the core region of the sample. The fracture models based on the effect of hydrogen on the degree of localized plastic deformation are proposed.