高周疲劳变形中二次孪晶与锥面位错之间的关系

Relationship between secondary twins and pyramidal dislocations in a Mg-3Al-1Zn alloy during high cycle fatigue deformation

摘要:

本文采用金相显微镜(OM),扫描电镜(SEM),透射菊池衍射(TKD)和透射电子显微镜(TEM)表征技术,研究了高周疲劳变形后的Mg-3Al-1Zn镁合金的典型断口组织特征,二次孪晶内部的横切面区域被提取出来进行TEM和TKD观察。结果显示断口边缘附近的区域有大量的{10-12}-{10-12}二次孪晶,双束明场技术(TBBF)应用于研究二次孪晶边界的位错类型。研究发现锥面位错在{10-12}-{10-12} 二次孪晶内部被大量的激活,这被认为锥面位错与二次孪晶有关联。二次孪晶内部的局部应力集中将导致锥面位错的形成。

Abstract:

Typical fracture morphology of Mg-3Al-1Zn alloy after cyclic deformation was investigated using optical microscope (OM), scanning electron microscopy (SEM), transmission Kikuchi diffraction (TKD) and transmission electron microscopy (TEM). Cross-section samples were extracted from secondary twin regions for TEM/TKD observation. The results showed that a large amount of {10-12}-{10-12} secondary twins were observed in the region near the fractured edge. Two-beam bright field (TBBF) technique was performed to study the types of dislocations along secondary twin boundaries. It was found that pyramidal dislocations were highly active within {10-12}-{10-12} secondary twins, which is considered to make pyramidal dislocations have the relationship with {10-12}-{10-12} secondary twins. Localized stress concentration within the secondary twins may lead to the formation of pyramidal dislocations.