预置粒子对镁合金动态再结晶及塑性改善的影响机理研究

Magnesium alloys are the lightest of all structural alloys, and currently receive great attention especially in the automobile industry. However, their low ductility and stretch formability at room temperature, due to their HCP structure, hampers their widespread application. We will propos a tentative idea of improving texture, to co-ordinate the contradiction between strength and ductility. The project aims to prepare a high-performance magnesium alloy with best combination of strength and toughness at low-cost and high-efficiency by a new method of "pre existing particle and hot-deformation". The effects of pre existing particle on the dynamic recrystallisation and the mechanism of improving ductility will be investigated by means of TEM and EBSD. The mechanism of interaction between the pre existing particle and dynamic recrystallisation, and their effect on texture evolution and mechanical properties will be especially focused. An ultimate goal of this project will be establishment of a new concept of grain refinement and improving texture through the coordinating role of the pre existing particle, twining and recrystallisation, and finally to realize toughening of magnesium alloy. This project can effectively improve the plasticity of magnesium alloy, it does not require any expensive material or rare earth element, nor does it require any additional processing. This work will further enrich and develop the theory of plastic deformation and recrystallisation of magnesium alloys and has great significance in low-cost preparation of high strength magnesium alloy with high plasticity.

针对镁合金十分突出的室温塑性低和强度不足的问题，本项目提出利用预置粒子协调变形，通过预置粒子与动态再结晶的交互作用来改善织构、平衡强度与塑性之间矛盾的设想。采用"预置粒子+高温变形" 低成本、高效率制备出具有最佳强韧配合的高性能镁合金。采用TEM和EBSD研究预置粒子对镁合金动态再结晶及其塑性改善机制的影响，深入揭示热变形过程中预置粒子与再结晶的交互作用机理及其对织构演化和力学性能的影响规律，并确立预置粒子、孪晶与再结晶协调细化晶粒、改善织构以及实现镁合金强韧化的新原理、新方法。本项目不需要昂贵的稀土或其它合金化元素，也不要增加额外的加工工序即可有效提高镁合金的塑性。这一工作将进一步丰富和发展镁合金的塑性变形与再结晶理论，并为今后探索低成本制备高强度和高塑性兼备的镁合金提供新思路和理论依据。

镁合金作为轻质结构材料备受关注，但较低的塑性、强度严重地制约了在交通运输、航空航天领域的大范围应用。本项目开发出“预置粒子+热变形”工艺，利用预置粒子与再结晶等，细化组织并调控织构，平衡镁合金塑性、强度之间的矛盾。同时，重点研究了预置粒子、再结晶、孪晶等之间交互作用，和其对组织、织构演化以及力学性能的作用机理。取得的主要研究成果有：(1) 揭示了该工艺下的变形行为及组织演变规律，阐明了第二相粒子与动态再结晶的交互作用，确立第二相与动态再结晶协同细化组织、调控织构及实现镁合金强韧化的新方法。(2) 揭示了不同工艺下热变形后第二相粒子分布、再结晶程度、晶粒取向与塑性、强度、抗蠕变性能之间的深层次关系并提出调控方法，为开发高性能镁合金提供指导。(3) 对镁合金进行中低温变形、退火等处理，利用第二相粒子、孪生变形及再结晶行为之间的交互作用，进一步阐明第二相粒子、孪晶或扭折带、细晶协同实现镁合金强韧化及高使役化的物理本质。本项目对稀土镁合金或其它合金化元素镁合金都可适用，所涉及变形及热处理工序皆为常见、常规手段，即可有效提高镁合金塑性、强度及使役性能。项目的研究成果丰富和发展了镁合金塑性变形与再结晶的理论，为高塑性、强度镁合金的低成本、高效率制备的提供新思路和理论指导。.上述研究成果发表学术论文15篇，获授权国家发明专利6项。