单轴应力场下钨中氦扩散行为的分子动力学模拟研究
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摘要
本文采用分子动力学方法研究了沿<100>及<111>晶向的单轴应变对钨中单个氦原子扩散的影响。结果表明,应变会使得金属钨材料发生相变,且引起相变的临界应变随温度升高而减小。相变起始的应变在达到抗拉强度的应变附近。计算结果表明,拉应变使得单个氦原子在钨中的扩散系数发生骤降,在不同应变下扩散系数变化平缓。沿<100>晶向氦扩散系数随应变的增大而线性减小,而<111>晶向则出现了震荡变化趋势。研究结果表明,沿<100>晶向应变达到+0.15%时阿纽列斯方程不再适用,而沿<111>晶向应变大+5%阿纽列斯方程仍然适用;沿<111>晶向随应变增加氦扩散激活能减小,说明应变使得单个氦原子在钨中迁移性增强。
The effect of uniaxial stress field along <100> and <111> crystal direction on the diffusion of a single helium atom in bcc tungsten was studied by molecular dynamics simulation. Our calculation shows that the stress strain caused the phase transition of tungsten metal and the initio phase transition strain decreases with the increase of temperature. The initial strain of phase transition is near the strain where stress reaches the maximum value. The diffusion coeffcient of a single helium atom in tungsten metal decreases with the increase of strain. The helium diffusion coeffcient decreases linearly along the <100> crystal direction, while the <111>crystal direction shows a fluctuating trend. Fitting the Arrhenius equation, the results show that when the crystal strain along <100> reaches +1.5% and the Arrhenius equation is no longer applicable; however, the Arrhenius equation still applies when the crystal strain along <111> increases by +5%. The helium diffusion activation energy along the crystal direction <111> was obtained, the results showed that the helium diffusion activation energy decreases with the increase of strain, indicating that the strain enhanceds the mobility of a single helium atom in tungsten.
The effect of uniaxial stress field along <100> and <111> crystal direction on the diffusion of a single helium atom in bcc tungsten was studied by molecular dynamics simulation. Our calculation shows that the stress strain caused the phase transition of tungsten metal and the initio phase transition strain decreases with the increase of temperature. The initial strain of phase transition is near the strain where stress reaches the maximum value. The diffusion coeffcient of a single helium atom in tungsten metal decreases with the increase of strain. The helium diffusion coeffcient decreases linearly along the <100> crystal direction, while the <111>crystal direction shows a fluctuating trend. Fitting the Arrhenius equation, the results show that when the crystal strain along <100> reaches +1.5% and the Arrhenius equation is no longer applicable; however, the Arrhenius equation still applies when the crystal strain along <111> increases by +5%. The helium diffusion activation energy along the crystal direction <111> was obtained, the results showed that the helium diffusion activation energy decreases with the increase of strain, indicating that the strain enhanceds the mobility of a single helium atom in tungsten.
引文
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