大变形高固溶Mg含量Al-Mg合金的纳、微米混晶组织形成及强塑性同时提高机制

To meet the great demands for low density, high-specific strength Al-Mg alloys in fields of aerospace, automobile and energy sessions, etc., the present project focuses on the key challenge that high-specific strength Al-Mg alloys processed by severe plastic deformation (SPD) usually have a low ductility, aiming to overcome the key difficulty in “achieving a simultaneous high strength and high ductility” for SPD Al-Mg alloys. The innovation of this project lies in the fact that by utilizing a combination of a moderate ECAP deformation strain and inter-pass annealing to improve the deformation ability of high solid solution Al-Mg alloys, promoting heterogeneous plastic deformation, forming nano-grains meanwhile achieving a multimodal grain structure, i.e., the coexistence of nano -, ultrafine- and micron grains. Considering that nano and submicron grains can lead to an increase in strength by grain boundary strengthening while the micron grains lead to enhanced work hardening and improved uniform ductility, an optimized nano/micron multimodal grain structure will be achieved by manipulating solute Mg content, ECAP and inter-pass annealing parameters. Moreover, adding trace alloying elements to form second-phase particles in binary Al-Mg alloys favors higher thermal stability of the nano/micron multimodal grain structure. The theoretical innovation of this project includes exploring the formation mechanism for the multimodal grain structure in the high solid solution Al-Mg alloys; clarifying the effect of nano/micron multimodal grain structure and high Mg solute content on mechanisms of the simultaneous increase in strength and ductility; exploring the effect of second phase particles on the recovery/recrystallization competition behavior; accordingly providing necessary theoretical basis for developments of new high strength (>550 MPa) and high ductility (>10 %) high solid solution (5-10 wt.%) Al-Mg alloys.

本项目面向空天、汽车和能源等领域对低密度高比强铝-镁合金的迫切需求，针对大变形铝-镁合金塑性差的关键科学问题开展研究，拟解决“强塑性同时提高”瓶颈难题。创新思路在于巧妙利用室温等通道角挤压（ECAP）结合中间退火提高高固溶Mg含量铝-镁合金室温变形能力，促进非均匀变形，获得多元尺度分布的纳、微米混晶组织。基于纳米晶细晶强化和微米晶促进加工硬化提高均匀延伸率的新机制，通过调控Mg含量和制备过程，优化纳、微米混晶组织，实现强塑性同时提高。通过添加微量元素（Sc、Zr等）形成第二相阻碍位错运动、抑制晶界迁移，提高纳、微混杂晶粒热稳定性。在理论上的创新：揭示高固溶Mg含量铝-镁合金中纳、微米混晶组织形成机制；阐明混晶组织特征和高固溶Mg含量对强塑性同时提高的作用机制；揭示第二相对纳、微米混晶组织回复/再结晶竞争行为的影响规律，为发展新型高强（>550MPa）高塑（>10%）铝-镁合金提供理论依据。

本项目面向空天、汽车和能源等领域对低密度高比强铝-镁合金的迫切需求，针对大变形铝-镁合金塑性差的关键科学问题开展研究，解决了“强塑性同时提高”瓶颈难题。创新思路在于巧妙利用热-力耦合变形加工，包括等通道转角挤压（ECAP）及大压下量衬板控扎技术（HPR），提高了高固溶Mg含量铝-镁合金的室温变形能力，促进了微观非均匀变形，实现了多元尺度分布的纳、微米混晶组织可控制备。基于纳米晶细晶强化和微米晶促进加工硬化提高均匀延伸率的新机制，通过调控Mg含量和变形加工参数，优化了纳、微米混晶组织特性，实现了强塑性同时提高。通过添加微量元素（Sc与Zr等）形成第二相阻碍位错运动、抑制晶界迁移，提高了混晶结构铝-镁合金的热稳定性。在理论上的创新：揭示出高固溶Mg含量铝-镁合金混晶结构组织形成机制及混晶铝-镁合金高温超塑性变形机制；阐明了混晶组织特征和高固溶Mg含量对强塑性同时提高的作用机制；揭示了混晶结构对组织热稳定的影响及第二相对混晶组织回复/再结晶竞争行为的作用规律，为发展新型高强（>550 MPa）高塑（>10%）高固溶（5-10 wt.%）铝-镁合金提供了理论依据。