Moisture-induced embrittlement mechanism for (Ni,Fe)Ti alloys

作者：Chen Yanfeng; Chung Yip Wah^*; Wen Hongmei

来源：Intermetallics, 2007, 15(3): 288-293.

DOI：10.1016/j.intermet.2006.07.002

• intermetallics, miscellaneous
• environmental embrittlement
• diffusion
• simulations, atomistic

Recent experimental studies showed that the ductility of NiTi is not affected by moisture, while addition of iron beyond 9 a/o in NiTi leads to moisture-induced embrittlement. To explore the nature of this embrittlement, we studied the chemical interaction between water vapor and (Ni,Fe) Ti(110) surfaces with 5 alo and 10 a/o Fe. Temperature-programmed desorption and X-ray photoelectron spectroscopy show that decomposition of water to produce atomic hydrogen occurs on both surfaces. Activation energy for surface diffusion was calculated by density functional theory, showing that addition of Fe decreases H surface diffusivity, in agreement with experiment. Together with the observation that addition of 9 alto Fe increases the strength of NiTi, this indicates that moisture-induced embrittlement in higher strength NiTi alloys is not due to faster H surface diffusion, but lower critical hydrogen concentration required for embrittlement.

• 出版日期2007-3
• 单位西北大学