本项目以国家航空航天、轨道交通等重点领域重大装备轻量化需求为导向，针对高强韧镁合金大规格变截面型材制备面临的变形抗力高、成形性差及组织性能不均匀等问题，提出“温度控制非对称、应力控制非对称、应变控制非对称”学术思路，融合反挤压技术，创新提出“差温反挤压、旋转反挤压、梯度应变反挤压”新型非对称反挤压技术思想，以自主研发的高强塑Mg-Gd-Y-Zn-Mn镁合金为研究对象，研究镁合金在不同温度场、应力场和应变场下塑性变形过程中位错滑移、孪生、再结晶、第二相演化的微观机理，通过数值模拟与实验相结合，弄清复杂应力条件下高强韧镁合金晶粒细化、织构弱化和强塑性调控规律，阐明高强韧镁合金成形及其组织性能调控机理，建立“非对称变形-微观组织-力学与成形性能”之间的构效关系，发展新型非对称反挤压对组织性能精准调控技术，获得高强韧镁合金大规格变截面型材高效制备技术原型，为高强韧镁合金关重件制备提供理论指导。

The project is guided by the demand for lightweight of major equipment in key areas, such as national aerospace and orbital transportation. To solve the problem of high deforming resistance, poor forming property, microstructure heterogeneity and non-uniform mechanical properties during preparing large-size variable cross-section profile of high-strength and high-ductility magnesium, we propose a new academic thought of "controlling asymmetry by temperature, stress and strain”. Combined with backward extrusion technology, a novel thought of asymmetric backward extrusion technology about "differential temperature backward extrusion, rotary backward extrusion, gradient strain backward extrusion" is put forward creatively. In this project, the self-developed high-strength and high-ductility Mg-Gd-Y-Zn-Mn alloys are taken as the research object to study the dislocation slip, twinning, recrystallization, and the evolution of the second phase of magnesium alloys during plastic deformation under different temperature, stress and strain fields. The mechanisms of grain refinement, texture weakening, controlling mechanical properties of the high-strength and high-ductility magnesium alloy under complex stress conditions would be clarified. The mechanisms of forming, regulation and controlling in structure and property of high-strength and ductility magnesium alloy would be illuminated through numerical simulation and experimentation. The structure-function relationship among “microstructure-asymmetric deformation-mechanical and forming property” would be established. A novel technique of asymmetric backward extrusion and the accurate regulating and controlling in structure and property would be developed. The technical prototypes of large-size variable cross-section profile preparation in high-strength and ductility magnesium alloy would be obtained, resulting in providing theoretical guidance for the fabricating and processing of high-strength and high-ductility magnesium which are served as key components in China.