氢原子渗透对管线钢微裂纹扩展的影响研究

管线钢在发生氢致开裂过程中，氢原子通过吸附、渗透等方式进入金属并聚集在微裂纹和微孔中，并与缺陷产生相互作用，对钢材的力学性能产生极大影响。为研究氢原子渗透对管线钢裂纹开裂行为的影响，采用分子动力学方法，首先建立含缺陷的铁素体型管线钢的铁素体-渗碳体微观片层结构，随后研究在单轴拉伸载荷作用下，处于300 K温度下不同氢原子浓度对铁素体-渗碳体层间裂纹扩展的影响，获取其力学性能曲线，并观察微观结构不同受载阶段的演化特征。结果显示，随着氢原子浓度的增加，铁素体-渗碳体片层结构的峰值应力将随之减小，且氢浓度越高，峰值应力降低幅度越大。氢原子的引入仅仅会改变裂纹扩展的速度，而不会对裂纹扩展方向产生变化。模型进入塑性应变时，大量位错及相变集中在裂纹右侧，从而阻碍右侧裂纹开裂，并且氢原子的引入也会阻碍FCC相和HCP相向BCC相的转变。研究可为深入探索管线钢氢致开裂行为的微观演化机理提供理论参考。

Effect of Hydrogen Atom Permeation on Microcrack Propagation of Pipeline Steel

In the process of hydrogen-induced cracking of pipeline steel, hydrogen atoms enter the metal by adsorption and infiltration, and gather in micro-cracks and micro pores, and interact with defects, which greatly affects the mechanical properties of steel. In order to study the effect of hydrogen atom permeation on crack behavior of pipeline steel, molecular dynamics method is used in this paper, the ferrite-cementite microstructure of ferrite pipeline steel with defects was established firstly. Then, under uniaxial tensile load at 300 K, the effects of different hydrogen atom concentrations on crack propagation between ferrite and cementite layers were studied, and the mechanical properties curves were obtained, and the evolution characteristics of microstructure at different loading stages were observed. The results show that with the increase of hydrogen concentration, the peak stress of ferrite-cementite lamellar structure will decrease, and the higher the hydrogen concentration, the greater the decrease of peak stress. The introduction of hydrogen atoms will only change the speed of crack propagation, but will not change the direction of crack propagation. When the model enters plastic strain, a large number of dislocations and phase transitions are concentrated on the right side of the crack, which hinders the crack cracking on the right side, and the introduction of hydrogen atoms also hinders the transition from FCC phase and HCP phase to BCC phase. The research can provide theoretical reference for further exploring the micro evolution mechanism of hydrogen-induced cracking behavior of pipeline steel.