镁合金中螺旋形织构形成机理与组织性能调控

Simultaneous enhancement of strength and ductility is one of the keys to the development of magnesium alloys. In the previously developed new technology called Online Torsion Extrusion by applicants, it can effectively refine grains of wrought magnesium alloys and form screw basal texture. The strength and plasticity are increased synchronously. However, crystallographic description of the screw basal texture is still unknown. At the same time, the formation mechanism and the deformation behavior of the screw basal texture also need a further study. In this project, the crystallographic description of the screw basal texture can be establish by investigating the 3D grain orientation of the screw basal texture. In order to reveal the microstructure characteristic and evolution during the online torsion extrusion process, the process is decomposed into axial extrusion strain and circumferential shear strain to obtain the regulating models of the screw basal texture and grain refining. The precise control of grain refining and texture spiraling of wrought magnesium alloys can be achieved. Uniaxial tensile and compression test are adopted to accurate analysis and characterize the deformation behavior (twining, dislocations slip) and microstructure evolution of the wrought magnesium alloys with screw basal texture. Seeking for the logic relationship and regulation mechanism between magnesium alloy structure and performance and establishing a plastic deformation theoretical model of wrought magnesium alloys with screw basal texture. Through the implementation of this project, the theoretical fundamental and experimental basis can be provided for the preparation of low-cost high-performance wrought magnesium alloys and the expansion of its application.

如何在提高强度的同时提高塑性是国内外镁合金发展的重点之一。申请人前期开发的在线扭转挤压新技术可有效细化镁合金晶粒，形成螺旋形的镁合金基面织构，达到同步提升强度与塑性的效果。但还缺乏螺旋形基面织构的晶体学描述，而螺旋形基面织构的形成机理以及其塑性变形微观机制的认识还远远不够。本项目将通过研究螺旋形基面织构三维晶粒取向特征，建立螺旋形基面织构的晶体学描述；将在线扭转挤压应变分解在轴向的挤压应变和周向的剪切应变，揭示在线扭转过程中镁合金挤压组织特性及演变规律，获得螺旋形基面织构与晶粒细化的调控模型，实现镁合金晶粒细化与织构螺旋化的精确控制；通过单轴拉伸、压缩实验对具有螺旋形织构的镁合金孪生、滑移变形行为及组织演变进行精确分析表征，寻求镁合金组织与性能之间的逻辑关系及调控机制，建立螺旋形织构组织的塑性变形理论模型。通过本项目的实施，为制备低成本高性能镁合金和扩大其应用提供理论基础及实验依据。

镁合金作为最轻的金属结构材料和优异的综合性能在很多领域具有重要的应用价值和广阔的应用前景。传统挤压或轧制工艺加工制得的镁合金板材具有强的基面织构，表现出差的力学性能。如何在提高强度的同时提高塑性是国内外镁合金发展的重点之一。本研究主要通过对所开发的在线扭转挤压工艺的优化，获得细化的镁合金晶粒，螺旋形的镁合金基面织构，获得强度、塑性与各向异性优异的镁合金材料。.1、以AZ31镁合金与ZK60镁合金为研究对象，深入研究了在线扭转挤压镁合金工艺参数对合金微观组织的影响，系统分析了工艺参数对性能的影响。.2、研究了在线扭转挤压参数对镁合金基面织构的影响，明确了螺旋形基面织构三维晶粒取向特征。.3、对典型的在线扭转挤压合金进行了制备过程中的组织结构特征的分析，获得在线扭转过程中镁合金挤压组织特性及演变规律，通过扭转速度与挤压速度的比值控制，实现了镁合金晶粒细化与基面织构的弱化。.4、对在线扭转挤压获得的镁合金材料的塑性变形机理进行了研究。重点分析了组织结构对合金强度以及各向异性的影响。