基于MD探究FeO/Fe中晶内微孔洞对FeO破裂的影响

氧化皮中的微孔洞直接影响着氧化皮的破裂性能。利用分子动力学(MD)模拟软件Lammps对含有微孔洞的FeO/Fe多晶模型进行拉伸模拟,研究了不同微孔洞数量情况下微孔洞尺寸对多晶FeO/Fe模型拉伸断裂的影响。研究发现,微孔洞数量相同时,FeO模型的抗拉强度随孔洞尺寸的增大呈现“下降→上升→下降”的趋势,表明了在一定范围内的孔洞尺寸会提高材料的抗拉强度,然而,此时的孔洞尺寸会降低材料的断裂韧性。中心对称参数CSP显示,原子紊乱程度由高到低的区域依次为孔洞处、晶界处、FeO/Fe界面处及FeO晶粒内部。研究结果为氧化皮的破裂机理提供了新的研究思路。

Effect of intra-crystalline micropores on FeO rupture in FeO/Fe based on MD

The micropores in oxide skin directly affects the cracking performance of oxide skin. Molecular dynamics simulation software Lammps was used to simulate the tensile fracture of FeO/Fe polycrystalline model with micropores. The effect of micropore size on tensile fracture of FeO/Fe polycrystalline model with different numbers of micropore was studied. The results show that the tensile strength of FeO model presents a trend of decreasing→increasing→decreasing with the increase of micropore size at the same number of micropores, indicating that micro-pore size in a certain range can improve the tensile strength of material, but the it can reduce the fracture toughness of material at the same time. CSP values show that the regions of atomic disorder degree from high to low are as follows of micropore, grain boundary, FeO/Fe interface and inside the FeO polycrystal. The results provide a new idea for the study of fracture mechanism for oxide skin.