高成形性Mg-Al-Zn/Mg-RE镁合金复合板非对称分流挤压的基础研究

镁合金板材作为重要的轻量化构件获得了广泛关注，而较低的室温成形性能限制了其进一步发展和应用。本项目提出通过非对称分流挤压制备高成形性能Mg-Al-Zn/Mg-RE异种镁合金复合板的新思路。挤压焊缝质量的控制和异种镁合金非均匀变形的协调是制备高质量复合板的关键。对此，本项目将结合物理模拟实验和数值模拟深入研究挤压条件对焊合质量的影响，分析表征焊合界面处的原子扩散、动态再结晶和界面金属间化合物的生成等微观组织演化特征，揭示异种镁合金挤压焊合机理，并在此基础上建立适用于异种镁合金的挤压焊合准则。通过数值模拟分析非对称分流挤压复合过程中金属流场和应变场，合理耦合异种镁合金变形的非对称特性和模具结构的非对称特性，调控异种镁合金的非均匀变形。最后，分析表征镁合金复合板的微观组织、力学性能和成形性能，建立挤压工艺参数、微观组织和成形性能之间的对应关系，为高成形性能镁合金复合板的开发提供理论基础和参考。

Magnesium alloy sheets have attracted more and more attention as a very promising material used for lightweight components. However, their wide application and development are limited due to the low formability at room temperature. In the present research, a new approach of asymmetric porthole die extrusion is proposed to produce high-formability Mg-Al-Zn/Mg-RE laminated composite sheet. The key of the method is to control the welding quality and coordinate the non-uniform deformation of the dissimilar magnesium alloys. With the importance, the present research will systematically investigate the effects of extrusion conditions on the welding quality of the magnesium alloys, by integrated methods combining physical experiments and numerical simulations. The evolution of microstructure at the welding interface, including the atomic diffusion, dynamic recrystallization, and generation of intermetallic compounds, will be studied to disclose the extrusion welding mechanism between dissimilar magnesium alloys. Based on the extrusion welding mechanism, a welding criterion will be established. Furthermore, numerical simulations will be conducted to investigate the deformation of the dissimilar magnesium alloys during the asymmetric porthole die extrusion. The asymmetric characteristics of the porthole die will be designed to coordinate the non-uniform deformation of the dissimilar alloys. Eventually, the microstructure, mechanical properties and formability will be evaluated to establish the relationship between the extrusion parameters and formability of the composite sheet. The findings will provide new technical ideas and theoretical basis for the development of magnesium alloy composite sheets with high formability.