镁合金变形孪晶界面迁移机制及其调控机理研究

{10-12} deformation twin plays an important role for magnesium alloys during plastic deformation at room temperature. However, the formation mechanism of {10-12} twin is still controversial, which significantly affects the process design, application and development of magnesium alloys. Understanding the mechanism of {10-12} twinning boundary migration and its control is crucial to interpret the behavior of {10-12} twin. In this program, multiple modern techniques, including electron back-scatter diffraction (EBSD) and transmission electron microscopy (TEM), of characterizing and analyzing materials will be employed to conduct a systematical study on the characteristics of {10-12} twinning boundary and lattice defects (such as dislocation and stacking fault). The features of {10-12} twinning boundaries are clarified. The control of basal-prismatic (BP/PB) interfaces and lattice defects on the migration of {10-12} twinning boundaries will be revealed. In the end, the mechanism of {10-12} twinning boundary migration will be clarified and combining with the theory of deformation twin and lattice defects, physical models on the growth of {10-12} twin and interaction between lattice defects and twinning boundary defects are expected to be established. Work to be carried out in this program can not only contribute much to the understanding on the mechanism of {10-12} twin in magnesium alloys, but also provide theory basis for the development of magnesium alloys with low cost and superior properties.

{10-12}孪晶变形是镁合金材料在室温变形条件下的主要变形机制。然而，学术界迄今对镁合金中{10-12}孪晶变形微观机理的理解存在很大争议，没有统一的解释，严重影响了镁合金材料的工艺设计、应用和发展。而研究{10-12}孪晶界面迁移特点及其调控机理对诠释{10-12}孪晶变形行为至关重要，因此，本项目拟采用包括电子背散射衍射、透射电子显微镜在内的多种表征技术手段，对镁合金中{10-12}孪晶界面和晶体缺陷特点进行表征和分析：明确孪晶界面微观结构特点，揭示基面-柱面（BP/PB）界面和晶体缺陷对孪晶界面迁移过程的调控机理，阐明{10-12}孪晶界面迁移机制，并结合孪生晶体学理论和晶体缺陷理论构建{10-12}孪晶长大模型和晶体缺陷与孪晶界面缺陷作用的位错反应模型。该课题的成功实施和开展，不但可丰富对镁合金中孪晶变形机制的认识，同时也可为发展低加工成本的高性能镁合金提供基础科学理论指导。

{10-12}孪晶变形是镁合金材料在室温变形条件下的主要变形机制。然而，学术界迄今对镁合金中{10-12}孪晶变形微观机理的理解存在很大争议，没有统一的解释，严重影响了镁合金材料的工艺设计、应用和发展。而研究{10-12}孪晶界面迁移特点及其调控机理对诠释{10-12}孪晶变形行为至关重要。本项目采用包括电子背散射衍射、透射电子显微镜在内的多种表征技术，对{10-12}孪晶的界面特点及影响迁移因素进行了研究。开展以下几个方面工作：（1）{10-12}孪晶界面的微结构特点的精细表征；（2）孪晶相互作用对孪晶界面迁移的影响；（3）孪晶和基体内部激活位错的类型和结构表征和确定；（4）镁合金{10-12}孪晶界面萌生微裂纹的微观机理。本项目的重要结果包括：（1）实际的{10-12}孪晶界面由CTB界面和BP/PB界面构成；（2）不同孪晶变体的相互作用可增加退孪晶的阻力，从而提高了宏观力学性能；（3）{11-22}孪晶内部的位错结构与基体中不同。基体中主要激活<a>位错，而孪晶内部可存在<c+a>位错；（4）由于孪晶内部位错与{10-12}孪晶界面的作用，导致界面处应力集中，从而诱发了孪晶界面微裂纹的萌生。该课题的成功实施和开展，不但可丰富对镁合金中变形孪晶机制的认识，同时也可为发展低加工成本的高性能镁合金提供基础科学理论指导。