镁合金{10-12}孪晶界面的精细结构及迁移过程的理论研究

Pre-{10-12} twinning become a low-cost machining and high performance for magnesium alloys. However, {10-12} twin boundaries (TBs) show very large deviations from the twinning plane, leading to {10-12} twinning mechanism is still controversial. In this program, HRTEM analysis technology will be employed, combining dislocation theory and twinning crystallographic theory, to study microstructure and migration process of {10-12} TB. The main research contents include: revealing morphology of {10-12} TB in AZ31 magnesium alloy under different strain condition; characterizing microstructure of CTB and BP/PB interfaces in {10-12} TB, and discussing effects of BP/PB interfaces for {10-12} TB deviating from twinning plane (K1); revealing details of atomic movement in TB, and building model of migration evolution model for TB, looking forward to clarify {10-12} twinning mechanism. Works to be carried out in this program can not only contribute much to the fundamental theory of {10-12} twinning deformation theory, but also provide the theory basis for the new mechanical technology of high-performance Mg alloys.

预置{10-12}孪晶作为开发低加工成本及高性能镁合金的有效途径。然而，学术界对{10-12}孪晶界面偏离其孪生面(K1面)的解释存在重大争议，导致对{10-12}孪生机制认识不清。考察孪晶界面精细结构对诠释孪生机制至关重要。因此，本项目重点采用HRTEM测试分析技术，结合位错理论和孪生晶体学等微观体系的理论研究手段，对镁合金{10-12}孪晶界面的精细结构及迁移过程进行基础科学研究。主要研究内容包括：揭示不同应变条件下对{10-12}孪晶界面宏观形态特征的影响规律；表征{10-12}孪晶界面（CTB和BP/PB）的精细结构，揭示BP/PB界面调控孪晶界偏离孪生面的物理本质；探讨{10-12}孪晶界面原子的移动细节，建立孪晶界的迁移演变模型，以期澄清{10-12}孪生机制。该课题的顺利开展，不仅可丰富{10-12}孪生变形基础理论知识，还可为探索高性能镁合金及其塑性加工新技术奠定理论基础。

表征{10-12}变形孪晶界面精细结构及探索其界面迁移行为，对深入理解{10-12}孪生行为具有重要的理论意义。本项目主要通过透射电镜表征{10-12}孪晶界精细结构，揭示了{10-12}孪晶界及其尖端的界面精细结构均由平行于晶体学上的{10-12}CTB和基面-柱面(BP/PB)界面构成。由于BP/BP界面的存在，使{10-12}孪晶界面偏离理论上的孪晶界面；且这种偏离的界面形态特征是{10-12}孪晶界的一种内在属性。基于孪生晶体和位错理论，孪生位错在CTB界面上滑动，随后通过“吸收-转化”过程，实现孪生位错在BP/PB的孪晶面上进行滑动，促使整个{10-12}孪晶界面迁移。该项目揭示了{10-12}孪晶界面偏离理论孪晶界面的根本原因，提供了{10-12}孪晶长大机制直接实验证据，丰富了{10-12}孪生变形基础理论知识。