H, O,P,S和N对金属Ni塑性形变机制影响的第一性原理研究

Effects of H, O, P, S and N impurities on the plasticity deformation mechanism of Ni by first-principles calculations

摘要:

本文基于密度泛函理论研究了H、O、P、S和N杂质以间隙式固溶于Ni(111)后对其变形能力的影响。发现：S、P在晶粒内部不稳定，不易存在于Ni(111)的间隙位置，而易向界面和表面扩散，H、O和N可在晶内分布，且N在Ni晶内分布的倾向性较大。对于Ni (111)<112>滑移系，P使得Ni层错能增大，而H、N、O、S降低了Ni的层错能，即H、N、O、S固溶于Ni使其沿(111)<112>滑移更为容易。总体来看，当外部环境介质H、N、O侵入到Ni基体时，由于使得体系的层错能降低，除产生的氧化、腐蚀等作用外，还使得该区域抵抗变形的能力下降，增大了蠕变变形的可能性。

Abstract:

The relationships between H, O, P, S, and N impurities and the type of plasticity mechanism displayed in Ni were studied using density functional theory. We found that different impurities have different segregation tendencies with regards to Ni. S, P, O, and H are most likely to occupy sites on the Ni surface, especially when S and P are the impurities. S, P, H and O have little effect on the deformation mechanism of Ni when located in the grains of the Ni metal. Conversely, N prefers to occupy these grains, readily promoting the dissociation of dislocation into segments, and making cleavage fracture less likely to occur, which enhances dislocation nucleation. S, P and N caused a decrease in the plasticity of Ni, but H and O increased the probability of twinning for Ni. However, these impurities do not switch the deformation mechanism of Ni from dislocation-mediated slipping to twinning.