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采用基于密度泛函理论的第一性原理方法,研究了氢原子对α-Fe力学性能的影响,对解析α-Fe氢脆本质做出了新的探索。氢掺杂使α-Fe的晶胞参数、氢原子周围铁原子的电荷以及Fe-H电子重叠数出现了各向异性的变化,从而导致α-Fe内聚力以及塑性各向异性。结果显示:沿[100]方向的内聚力在高氢浓度(HFe4)时明显增大,但其在较小的塑性变形下就达到峰值,随后随塑性变形的增加明显降低,说明氢掺杂使铁塑性降低;沿[001]方向的内聚力逐渐降低,使该方向的断裂韧性降低,导致铁在低应力下产生断裂。根据这些研究结果,认为[100]方向塑性的降低以及[001]方向断裂韧性的降低是导致α-Fe氢脆断裂的主要原因。
The first-principle method based on density functional theory (DFT) was used to study the influence of hydrogen atoms on the mechanical properties of α-Fe, and a new exploration was made to resolve the hydrogen embrittlement of α-Fe. Hydrogen doping changes the unit cell parameters of α-Fe, the charge of iron atoms around hydrogen atoms and the number of overlap of Fe-H electrons, resulting in the cohesion and plastic anisotropy of α-Fe. The results show that the cohesive force along the [100] direction obviously increases at high hydrogen concentration (HFe4), but it reaches its peak under the small plastic deformation and then decreases with the increase of plastic deformation. Plasticity decreases; cohesion along the [001] direction gradually decreases, so that the fracture toughness of the direction decreases, resulting in low-stress iron fracture. According to these results, it is considered that the decrease of plasticity in [100] direction and the decrease of fracture toughness in [001] are the main reasons leading to hydrogen embrittlement fracture of α-Fe.