氢原子对双晶α-铁晶界裂纹扩展影响的模拟研究

Simulations on effect of hydrogen atoms on crack propagation of double crystal α-Fe

为从微观角度研究氢原子对α-铁力学行为的影响,并解释α-铁在形变过程中材料微结构演化的细节与规律,采用分子动力学模拟方法研究在拉伸载荷下,氢浓度对含有对称斜晶界的双晶α-铁裂纹扩展的影响。计算结果表明:双晶α-铁的峰值应力随着氢浓度的增加而减小。由于左右裂纹晶向的不同,致使裂纹不对称的开裂。研究发现,氢原子会阻碍裂纹扩展,但氢原子对左右裂纹阻碍的机制不同。研究结果显示,氢原子聚集在左裂纹尖端,增强裂纹尖端区域的局部塑性,阻碍裂纹向左侧的扩展;然而,裂纹右侧区域的氢原子不仅增强裂纹尖端的局部塑性,还促进Hirth位错在右裂纹尖端相变区域的成核,从而有效阻碍右裂纹扩展。

In order to study the effect of hydrogen atom on the mechanical behavior of α-Fe,and to explain the details of the evolution of microstructure during deformation process,the effects of hydrogen atoms on the crack propagation behavior of bicrystal α-Fe with symmetric tilt grain boundaries under tension loading were investigated by molecular dynamics simulations.The computational results show that the peak stress of bicrystal α-Fe decreases with the increase of hydrogen concentration. Due to the different crystallographic orientation of cracks,the crack growth behavior of the bicrystal is governed by different deformation mechanisms. The studies find that the hydrogen atoms may prevent crack propagation,and the mechanisms are different for the left and right cracks. The results show that the hydrogen atoms gathered in the left crack tip enhance the local plasticity in crack tip region and hinder the expansion of the cracks to the left;However,the hydrogen atom on the right side of the crack not only enhances the local plasticity of the crack tip,but also promotes the nucleation of the Hirth dislocation at the right crack tip phase transition region.