Xiaoying CHENG
,
Xiaojing WAN
,
Qiuyun WU
,
Xiukui SUN
材料科学技术（英）
The diffusivity of hydrogen in two Ni3Al alloys (No.1 and No.2) has been measured in the temperature range of 100℃ to 420℃ using an ultrahigh vacuum gaseous permeation technique. The diffusivity data fall into two segments, in which the hydrogen diffusivity adheres to the Arrhenius form, respectively. From the hydrogen diffusivity, it is conjectured that the hydrogen diffusivity reflects the hydrogen transportation along the grain boundaries at lower temperature and the hydrogen transportation in the lattice at higher temperature. The intergranular fracture of Lit-type intermetallics induced by hydrogen at relative low temperature results from hydrogen transportation along the grain boundaries and not in the lattice.
关键词:
Xiaoying CHENG
,
Xiaojing WAN
,
Yexin CHEN
,
Meiyi YAO
材料科学技术（英）
Some observation relating tp the solubility, diffusivity and intergranular cracking by hydrogen transport from the external surface in Co3Ti, Co3Ti-Al and Co3Ti-Fe alloys have been carried out. The results show that the addition of alloying elements Al or Fe to Co3Ti alloy can increase the critical hydrogen concentration for changing from transgranular to brittle intergranular fracture, therefore suppress the moisture induced environmental embrittlement.
关键词:
Yexin CHEN
,
Xiaojing WAN
,
Weixin XU
材料科学技术（英）
The interaction of water vapor and oxygen with TiAl-based alloy has been studied with Auger electron spectroscopy and X-ray photoelectron spectroscopy. The results indicate that both surface reactions initiate at a very short exposure (about 6×10(-7) Pa·s) and the oxides Al2O3 and TiO2 form in the surface reactions. In the oxidizing reaction, the water vapor reacts firstly with Al, and then reacts with Ti after certain exposure. The surface reaction of Al with water vapor may be responsible for the environmental embrittlement at room temperature in TiAl-based alloy.
关键词:
Surface reaction
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,
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