Study of microcrack nucleation from a blocked twin with the wedge disclination model
Study of microcrack nucleation from a blocked twin with the wedge disclination model
复制标题
用楔形向错模型研究块孪晶的微裂纹形核
DOI：
10.1007/s00419-016-1177-x
复制
发表时间：
2017-01-01
影响因子：
2.8
通讯作者：
Luo, J.
中科院分区：
文献类型：
--
作者：
Luo, J.
孪晶是晶体材料的一种重要变形机制。变形孪晶在晶界处的阻塞会导致微裂纹形核，严重影响材料的力学性能。本文提出了一个理论模型来研究在晶界处由阻塞孪晶引起的微裂纹形核。变形孪晶用楔向错四极模型模拟。从最近的分子模拟结果的启发，微裂纹被假定为有两个尖锐的尖端和形核的负楔向错的拉伸应力之一。然后用分布位错法揭示了形核裂纹的特征。讨论了远向错偶极子对裂纹形核的影响。研究发现，对于大长径比的孪晶，向错偶极子模型足以模拟裂纹形核行为。计算了形核裂纹的张开轮廓，并与文献中的原子模拟结果进行了比较。数值结果表明，对于特定的形变孪晶，存在一个微裂纹形核的临界孪晶厚度。该模型可以预测孪晶的临界厚度。
Twinning is an important deformation mechanism of crystalline materials. A deformation twin blocked at the grain boundary may lead to microcrack nucleation and seriously deteriorate the mechanical properties of materials. In this paper, a theoretical model is proposed to study the microcrack nucleation from a blocked twin at the grain boundary. The deformation twin is simulated with the wedge disclination quadrapole model. Inspired from the recent molecular simulation results, the microcrack is assumed to have two sharp tips and nucleate from the tensile stress of one of the negative wedge disclinations. The characteristics of the nucleated crack are then revealed with the distributed dislocation method. The influence of the remote disclination dipole on the crack nucleation is discussed. It is found that for twins with large aspect ratios, the disclination dipole model is sufficient to simulate the crack nucleation behavior. The opening profile of the nucleated crack is calculated and is comparable with the atomistic simulation result in the literature. The numerical results indicate that for a specific deformation twinning, there exists a critical twin thickness for the microcrack to nucleate. The critical thickness of the twin can be predicted with the proposed model.