基于强化动态再结晶和纳米析出相调控制备高强高塑镁合金板材方法的探索

Wrought magnesium alloy sheets with high strength and high plasticity have wide applications in the fields of aerospace, armament systems, automobile and etc.due to their excellent plastic formability for complex thin-walled structure parts.How to improve both the strength and the plasticity of these sheets is a diffficult problem in the field of magnesium alloys. The applicants propose that the wrought magnesium alloy sheets with high strength and high plasticity can be prepared by the combination of micro-alloying and high stain rate rolling. Dynamic recrystallization induced by twin nucleation can be enhanced to achieve grain refinement and nanometer precipitates are induced during high stain rate rolling. The features of nanometer precipitations such as type, size, precipitation density, morphology and etc can be modified by microalloying and rolling parameters. On the basis of the investigations mentioned above, a novel method for the preparation of the bulky superfine grained especially the nanocrystalline magnesium alloy sheets with high strength and high plasticity will be explored. The influences of micro-allloying and high stain rate rolling on grain refinement, the modification of nanometer precipitates, strength and plasticity of the as-prepared sheets and their action mechanisms will be systematically studied. The precipitation mechanism of the nanometer precipitates will be elucidated. The interactions between the nanometer precipitates and the deformation mechanisms such as twinning, dynamic recrystallization nucleation and growth will be clarified. The corelations of strength and plasticity to grain size and the feature of nanometer precipitates will be explored. Moreover, the stamping performance of the superfine grained magnesium alloy sheets will be also explicited. The project will provide the scientific grounds and accumulate the experimental data for the preparation of the the nanocrystalline wrought magnesium alloy sheets with high strength and high plasticity.

高强高塑镁合金板材在高性能复杂薄壁结构件塑形加工成形方面具有明显的工艺及性能优势,在航空、航天、国防军工、汽车等领域具有极其重要的应用价值。如何在提高板材强度的同时改善其塑性是目前镁合金材料研究领域的一大难题。申请人提出将微合金化和高应变速率轧制相结合制备高强高塑变形镁合金板材,通过高应变速率变形来强化动态再结晶以最大限度地细化晶粒和诱导纳米相析出，通过轧制工艺和微合金化调控纳米析出相特征包括类型、尺寸、分布和形貌等,藉此探索一条开发超细晶粒高强高塑变形镁合金板材的新途径。系统研究微合金化和高应变速率轧制对镁合金晶粒细化、纳米析出相调控、强度和塑性的影响规律及作用机制，揭示纳米析出相的析出机制，探明纳米析出相与孪生变形、动态再结晶形核和长大的交互作用，阐明合金强度、塑性与晶粒尺寸和纳米析出相特征的相关性，探明超细晶板材的冲压成形性能，为新型高强高塑变形镁合金板材研制提供科学基础和实验依据。

高强高塑变形镁合金板材具有优异的力学性能及塑形成形性能，在高性能复杂薄壁结构件的塑形成形方面具有明显的工艺及性能优势，在航空、航天、国防军工、汽车、电子等领域具有重要的应用价值和广阔的应用前景。但如何实现此类板材的工业化生产是一项技术难题。本项目选取了Mg-Zn-Zr和Mg-Zn-Mn系镁合金中的典型牌号ZK60、ZM51、ZM61和Mg-5Zn合金为研究对象，选择的微合金化元素有Sn、Sr、Ca 、Y、Gd，系统研究了高应变速率轧制工艺及参数、微合金化元素等影响动态再结晶过程、纳米沉淀相动态析出的规律及机制，通过系统的实验研究和深入的理论分析，获得了一系列重要成果：探明了高应变速率变形、微合金化处理单独或耦合强化动态再结晶过程和纳米沉淀相析出的规律及机制，发展了纳米沉淀相及动态再结晶晶粒尺寸的调控方法，实现了对板材微观组织(包括纳米析出相特征和晶粒尺寸)及性能的精确调控，探索出了一种高效制备高强高塑变形镁合金细晶板材的短流程新工艺，优化出了最佳轧制工艺参数范围；探明了纳米沉淀相的析出规律及机制，阐明了纳米析出相与孪生变形和动态再结晶的交互作用规律及机制，为高强高塑镁合金板材的研制提供了科学基础；揭示了高应变速率轧制镁合金板材的强度、塑形与晶粒尺寸和纳米析出相特征的关系，明确了板材实现高强高塑的晶粒尺寸范围和纳米析出相特征，评价了其塑性成形性能特别是冲压性能，为新型高强高塑变形镁合金板材的实际应用积累了大量实验数据。