基于液-固协同调控的新型高固溶多元镁-铝系合金组织控制及强塑性同时提高机制

The present project focuses on a key challenge that Mg alloys usually suffer from low strength and low room-temperature ductility, achieving microstructure refinement and weakened texture based on novel liquid-solid co-regulation fabrication route, i.e. coupling near-rapid solidification technique and asymmetrical controlled rolling, aiming to make a breakthrough on the key difficulty, i.e. achieving a simultaneous high strength and high ductility, for Mg alloys. The innovation of this project lies in the fact that the sophisticated combination of novel high solid solution alloy design and near-rapid solidification technique, achieving high solid solution microstructure control and exploring the mechanism for microstructure formation and evolution; achieving grain refinement of the high solid solution alloy matrix and precipitates dispersion as well as basal texture weakening based on asymmetrical controlled rolling. Based on the fact that the fine grain structure and dispersed fine precipitates together with weakened basal texture favor for enhanced work hardening, while fine grain structure and dispersed fine precipitates promote superplasticity of Mg-Al alloys, realizing a complete control of high solid-solution microstructure - high strength and ductility in multi-alloying Mg-Al-system alloys. The theoretical innovation: revealing the influence of high level solid solutes and precipitates on the formation and evolution of fine grain structure and weak texture as well as the regulation mechanism of high strength and ductility of high solid solution Mg alloys; providing necessary basis for the development of novel high strength and ductile Mg alloys with (room temperature tensile strength > 370MPa, yield strength > 240MPa, elongation > 15%, 300oC elongation > 600%).

本项目针对镁合金强度低、室温塑性差关键科学问题，耦合亚快速凝固高固溶组织与非对称异步控轧，基于液、固协同调控新思路实现Mg-Al系合金组织细化及织构弱化协同调控，旨在“强塑性同时提高难”瓶颈难题上取得突破性进展。创新思路在于将高固溶多元镁合金设计与亚快速凝固巧妙结合，实现新型多元Mg-Al系合金高固溶凝固组织控制并揭示其形成、演化规律及调控机制；基于非对称异步控轧实现新型高固溶组织细化、析出相弥散及织构弱化协同调控；基于细晶组织和弱基面织构促进镁合金加工硬化、室温强塑性同时提高和高温超塑性变形机制，实现Mg-Al系合金高固溶组织-高强塑性能一体化调控。在理论上的创新：阐明高含量溶质与析出相对高固溶镁合金细晶组织、弱织构形成与演化的影响规律及高强塑性调控机制；为发展新型高强塑性镁合金（室温强度>370MPa、屈服>240MPa、延伸率>15%、300oC拉伸应变>600%）提供借鉴。

本项目针对高Al含量Mg-Al合金中粗大网状脆性共晶相 Mg17Al12 难以断网这一瓶颈难题，基于多元合金设计思路引入Sn、Zn、Ca、RE 等主、微合金元素，采用亚快速凝固技术提高微合金元素固溶度。揭示了亚快速凝固冷速条件下（100 -1000K/s）多元共晶相析出行为及演化规律；阐明了微合金元素对基体及共晶相细化的影响规律；揭示了亚快速凝固下新型多元Mg-Al系合金高固溶组织形成、演化规律及调控机制。. 本项目揭示了粗大微米级相提供的动态再结晶（DRX）驱动力与亚微米级相的Zener钉扎阻力对控轧过程中Mg-Al 合金DRX形核、晶粒长大以及织构演化的影响规律，实现了混晶组织中细晶比例优化与织构弱化协同控制；发现具有较高细晶比例的AZ91-1Y合金具有最佳强塑性结合（抗拉强度为~405 MPa、延伸率为~9.4%）；揭示了粗晶、细晶区域织构特性及其对塑性变形影响机制。. 本项目通过短流程控轧制备了新型非均匀层片结构AZ91-1Sn镁合金，拥有优异的加工硬化能力和良好的强-塑性协同（抗拉强度高达~393 MPa，延伸率~23%）；揭示了在晶界向错和晶间位错滑移传递的介导作用下，多种难激活变形模式大量开启从而显著提高塑性和加工硬化能力的异质层间异构强化机制。. 通过本项目研究，实现了新型多元Mg-Al系合金高固溶凝固组织控制，为新型高性能Mg-Al系合金设计提供借鉴；阐明了高含量溶质与析出相对高固溶镁合金细晶组织、弱织构形成与演化的影响规律及高强塑性调控机制,为混晶结构镁合金组织与织构协同调控实现强塑性同步提升提供依据；提出了一种有效的高性能镁合金异质结构设计策略，为基于拓扑缺陷理论理解异质结构材料的变形行为和力学性能提供了新的视角。

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