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建立了Fe-C合金晶格模型,利用分子动力学方法研究了在5K温度下Fe-C合金体系的能量分布和C原子对Fe-C合金晶格结构的影响;分别对纯Fe和Fe-C合金体系进行了单轴拉伸试验,得到了两种情况下的应力-应变曲线;结合径向分布函数、共同近邻分析、原子构型演化分析等方法,研究了C原子对Fe-C合金拉伸性能的影响。得到以下结论:C原子使得Fe-C合金体系平均势能降低,晶格常数扩大;在单轴拉伸过程中,C原子的存在使Fe-C合金体系产生了结构上的不均匀性,在体系内部存在局部应力相对较大区域,位错滑移带首先在C原子影响区域产生,并且诱发了体心立方结构向面心立方结构或六角密排结构(bcc→fcc/hcp)的转变,从而导致了体系强度的降低;C原子影响区域本身就是结构中较为脆弱的部分,结合相变区域的影响,所以Fe-C合金更容易发生破坏断裂。
The lattice model of Fe-C alloy was established. The energy distribution of Fe-C alloy system and the effect of C atom on the lattice structure of Fe-C alloy at 5K were investigated by molecular dynamics method. C alloy system was uniaxial tensile test, the stress-strain curve of the two cases was obtained. Combining the radial distribution function, common neighbor analysis and atomic configuration evolution analysis, the effect of C atom on the Fe-C alloy Tensile properties. The results show that the average potential energy of Fe-C alloy system decreases and the lattice constant increases due to the C atom. In the uniaxial stretching process, the presence of C atom causes structural inhomogeneity in the Fe-C alloy system. Dislocation slip band first occurs in the C atom influence region and induces the transformation of body-centered cubic structure to face-centered cubic structure or hexagonal close-packed structure (bcc → fcc / hcp) Resulting in a decrease of the strength of the system. The C atom influence region itself is the more fragile part of the structure. Therefore, the Fe-C alloy is more prone to fracture failure due to the influence of the phase transition region.