材料期刊网

对理想晶体中的H扩散通量与充H时间的关系式进行修正, 并用修正后的公式直接从实验数据中拟合H在材料中的扩散系数和穿透时间, 结果表明, 用理想晶体中H扩散通量随充H时间变化的修正关系式可以表征实际材料在电化学充H过程中的H原子扩散通量随充H时间变化的关系曲线, 也可以用以研究实际材料中H陷阱对H原子扩散系数的作用. 用修正后的公式对20g纯净钢电化学充H实验数据进行最小二乘法拟合, 直接得到H原子在不同H陷阱状态20g纯净钢中的扩散系数和穿透时间. 拟合结果显示: 20g纯净钢中的不可逆H陷阱对H原子的扩散系数没有影响, 只是延长了H原子的穿透时间, 而可逆H陷阱则降低了H原子的扩散系数.

Electrochemical permeation experiment is the most common method used in measuring hydrogen diffusivity. Because the effect of hydrogen traps has been ignored, there is a larger deviation between diffusion coefficients of hydrogen given by many investigators, especially at low temperatures. In order to study the effect of hydrogen traps on diffusion coefficient of hydrogen, the permeation current transients were measured by Devanathan-Stachurski cell for the three hydrogen trap states in 20g clean steel in this paper. The first trap state contains the inreversible and reversible hydrogen traps and exists in an original state of the sample. The second trap state contains only the reversible hydrogen traps and exists in the sample treated at 80 ℃ for 3 h after electrochemical permeation experiment. However, the third trap state may not contain any hydrogen traps and exists in the untreated sample after the electrochemical permeation experiment. The electrochemical permeation experiment has been carried out at a constant charging current density (10 mA/cm²) in\linebreak 0.2 mol/L NaOH solution at 30 ℃. The experimental results show that the diffusion of hydrogen in electrochemical hydrogen permeation can be described by a modified equation of diffusion flux versus time in ideal crystal. The modified equation proposed in this paper is $\frac{J_{t}}{J_{\infty}}=\frac{2L}{\sqrt{\pi D(t-t_{0})}}\sum\limits_{n=0}^{\infty}exp
[-\frac{(2n+1)^{2}L^{2}}{4D(t-t_{0})}]$. The diffusion coefficient and penetration time of hydrogen during electrochemical hydrogen permeation can be obtained directly by using the modified equation to fit the experimental data with a least square method. The experimental results reveal that inreversible hydrogen traps have no effect on the diffusion coefficient of hydrogen, but extend its penetration time. It is also shown that reversible hydrogen traps reduce the diffusion coefficient of hydrogen in 20g clean steel.