体心立方Ta的广义面错能及在Ⅱ型裂纹尖端初始塑性研究中的应用  

Generalized planar fault energy of body-centered cubic Ta and its application to plastic deformation of mode Ⅱ crack tip

作　　者：梅继法[1] 黎军顽[1] 倪玉山[1] 王华滔[1] 

机构地区：[1]复旦大学力学与工程科学系,上海200433

出　　处：《物理学报》2011年第6期506-513,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:10576010) 资助的课题~~

摘　　要：基于嵌入原子势考察体心立方(bcc)金属Ta的广义层错能和广义孪晶能并获得广义层错能和广义孪晶能曲线.研究表明,bccTa的广义层错能曲线与面心立方金属的广义层错能曲线有明显差异,Ta的广义层错能曲线不存在明显的能量极小值,位错主要以全位错的形式发射.不同原子厚度的广义孪晶能曲线表明4个原子层的孪晶能曲线开始出现亚稳定的能量极小值,5个原子层的孪晶能曲线出现稳定的能量极小值.为进一步验证广义层错能和广义孪晶能曲线揭示的塑性变形机理,采用准连续介质力学多尺度方法研究Ⅱ型裂纹尖端的初始塑性变形过程.结果表明,变形孪晶和全位错发射同为Ⅱ型裂纹尖端两种重要的塑性变形机理.The generalized planar fault energy,including the generalized stacking fault（GSF） and the generalized twinning fault energy（GTF） of body-centered cubic metal Ta are investigated based on the embedded atom potential.The GSF of Ta,much different from that of fcc metal,reveals that no evident energy minimum is observed in the energy curve.This implies that only full dislocations are possibly emitted in the {112} slip plane.From the GTF it is predicted that the minimum thickness of a metastable twin is as large as four layers and the five-layer twin is more stable.The incipient twin Ta tends to grow thicker once it is created.To confirm the significance of the GSF and GTF in revealing incipient plasticity,quasicontinuum method is used to simulate the mode Ⅱ crack of single Ta crystal.The results show that deformation twin and full dislocation along 111 direction in {112} plane are two co-existing mechanisms of crack tip plastic deformation.The initial four-layer twin quickly extends into five-layer and more-layer twins with further loading.A full dislocation is emitted into the front of the crack tip in {112} plane.These two plastic deformation mechanisms are well explained by the GTF and the GSF respectively.

关 键 词：广义层错能 广义孪晶能 体心立方金属钽 Ⅱ型裂纹 

分 类 号：O482.1[理学—固体物理]