原子模拟钛中微孔洞的结构及其失效行为  

Atomistic simulation of microvoid formation and its influence on crack nucleation in hexagonal titanium

作　　者：何燕 周刚[1,4] 刘艳侠[5] 王皞 徐东生[1] 杨锐[1] 

机构地区：[1]中国科学院金属研究所,沈阳110016 [2]中国科学院大学,北京100864 [3]沈阳师范大学物理科学与技术学院,沈阳110034 [4]大连理工大学材料科学与工程学院,大连116024 [5]辽宁大学物理学院,沈阳110036

出　　处：《物理学报》2018年第5期21-27,共7页Acta Physica Sinica

基　　金：国家重点基础研究发展计划(批准号:2016YFB0701304);国家自然科学基金(批准号:51671195;11674233;61603265);沈阳师范大学科技项目(批准号:L201521)资助的课题~~

摘　　要：六角金属由于其各向异性等特点,在塑性变形等过程中容易产生形状和构型都相对复杂的点缺陷团簇.这些团簇之间及其与运动位错等缺陷的相互作用直接影响材料的物理和力学性能.然而对相关问题的原子尺度、尤其是空位团簇的演化和微孔洞的形成乃至裂纹形核扩展等的理解还不全面.本文采用激发弛豫算法结合第一原理及原子间作用势,系统考察了钛中的空位团簇构型及不同构型间的相互转变,给出了不同尺寸空位团簇的稳定和亚稳构型、空位团簇合并分解和迁移的激发能垒等关键参数,发现较小的空位团簇形成稳定构型,较大的空位团簇呈现出空间对称分布趋势进而形成微孔洞;采用高通量分子动力学模拟系统研究了不同尺寸的空位团簇在拉应力作用下对变形过程的影响,发现这些空位团簇可以形成层错,并对微裂纹的形核产生影响.During the plastic deformation of hexagonal metals, it is easy to generate the point defect clusters with complex shapes and configurations due to their anisotropic properties. The interactions among these clusters and between these clusters and moving dislocations significantly influence the physical and mechanical properties of hexagonal materials.However, none of these issues in particular concerning the evolutions of vacancy clusters, the formation of microvoids,and the crack nucleation and propagation, is comprehensively understood on an atomic scale. In the present work, we first employ the activation-relaxation technique, in combination with ab initio and interatomic potential calculations, to systematically investigate vacancy cluster configurations in titanium and the transformation between these clusters. The results indicate the stable and metastable configurations of vacancy clusters at various sizes and activation energies of their dissociation, combination and migration. It is found that the formation and migration energies decrease with the size of vacancy cluster increasing. Small vacancy clusters stabilize at configurations with special symmetry, while large clusters transform into microvoids or microcracks. High-throughput molecular dynamics simulations are subsequently employed to investigate the influences of these clusters on plastic deformation under tensile loading. The clusters are found to facilitate the crack nucleation by providing lower critical stress, which decreases with the size of the vacancy clusters increasing. Under tensile loading, cracks are first nucleated at small clusters and then grow up, while large clusters form microvoids and cracks directly grow up.

关 键 词：原子模拟 力学性能 空位团簇 裂纹 

分 类 号：O469[理学—凝聚态物理]