含氢原子缺陷晶界的剪切行为  

SHEAR RESPONSE OF GRAIN BOUNDARIES WITH HYDROGEN DEFECTS

作　　者：赵东伟[1] 郁汶山[1] 申胜平[1] Zhao Dongwei;Yu Wenshan;Shen Shengping(State Key Laboratory for Strength and Vibration of Mechanical Structures,Shanxi Engineering Laboratory for Vibration Control of Aerospace Structures,School of Aerospace,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]西安交通大学航天航空学院机械结构强度与振动国家重点实验室/陕西省航天结构振动控制工程实验室,西安710049

出　　处：《力学学报》2017年第3期605-615,共11页Chinese Journal of Theoretical and Applied Mechanics

基　　金：国家自然科学基金资助项目(11502191;11372238;11632014)

摘　　要：针对4个α-Fe对称倾斜晶界,采用分子静力学考察了4个晶界中H原子偏析能的分布特征,并采用分子动力学方法研究了晶界内植入不同数量H原子对其在室温条件下剪切行为的影响.H原子通过随机方式植入界面内,利用植入H原子数量与晶界面积的比值来定义H原子面密度ρ.在含H原子晶界剪切行为分析过程中,重点考察了在不同H原子密度ρ下,4个晶界的初始塑性临界应力和晶界迁移位移的变化趋势以及4个晶界在加载过程中的微观变形机理.研究表明:晶界内的H原子偏析能明显偏低,4个晶界附近的H原子会自发向晶界内偏析;随着植入H原子数量的逐渐增多,晶界的初始塑性临界应力和后续变形阶段应力均会降低.晶界内植入H原子会从本质上改变晶界的微观变形机理,进而影响晶界在外载荷条件下的迁移属性.与不含H原子晶界的变形机理对比发现,加载过程中晶界的微结构会发生剧烈的演化,H原子的扩散和团簇化效应会导致晶界内出现纳米孔缺陷.The segregation energy distributions of hydrogen in four_-Fe symmetric tilt grain boundaries(GBs)are analyzed by using molecular statics(MS),and then the shear responses of four GBs embedded with di_erent number of hydrogen atoms at the room temperature are investigated by using molecular dynamics(MD)methods.To facilitate our quantitative analysis,the hydrogen density_is defined as the ratio between the number of hydrogen atoms and the GB area.At di_erent hydrogen densities,the variations of initial critical stress of GB plasticity and GB migration displacements are analyzed,and the micro-deformation mechanisms in each GB with the presence of hydrogen atoms are analyzed as well.It is found that the hydrogen segregation energies are generally lower in GB than those inside grain,which lead four GBs to absorb hydrogen atoms in the vicinity of GBs.With the increase of hydrogen density_the critical stress of incipient plasticity as well as the flow stress could be reduced.Moreover,the micro-deformation mechanisms of fours GBs with hydrogen atoms are di_erent from those of GBs without hydrogen atoms.In particular,presence of hydrogen atoms remarkably a_ects GB migration velocity.Thus,GB with hydrogen atoms may undergo a pure sliding deformation instead of the shear-coupling deformation for GB without hydrogen atoms.Meanwhile,in contrast to GBs without hydrogen atoms,the micro-structures of GB with hydrogen atoms drastically evolve upon loading.In addition,the di_usion and agglomeration of hydrogen atoms may lead to the formation of nanovoid in GBs.

关 键 词：晶界 氢原子 偏析能 剪切行为 

分 类 号：O341[理学—固体力学]