原位自生纳米准晶增强Mg-Zn-Er合金超塑性研究

Aiming at the problem of the effect of lack of thermal-stable pinning particles on the superplastic forming of the magnesium alloys materials at a high strain rate, the present project aims to produce the M-Zn-Er alloys reinforced with the precipitate of the nano-scale I-phase in-situ activated by stress concentration via multi-direction rolling at relative low temperature. Considering the factors of stress, temperature and composition, the kinetic characteristic of the nucleation and growth of the nano-scale I-phase will be investigated by HRTEM and HAADF-STEM etc. in order to find the formation mechanism of the nano-scale I-phase. At the same time, the interaction of the nano-scale I-phase with the matrix, dislocation and interface will be investigated by TEM in-situ to expound the effect of the nano-scale I-phase on superplastic behaviors. Moreover, from the view point of micron/ nano scale, the effect of the nano-scale I-phase on the microcracks and cavities will be investigated so as to reveal the failure mechanism of the alloys during superplastic deformation at a high strain rate. The project will provide a kind of scientific principle for the design of magnesium alloys reinforced with the thermal-stable particles, which can be used as a type of materials for superplastic forming at a high strain rate.

针对因缺乏热稳定粒子影响了镁合金材料在高应变速率下的超塑性成形这一问题，本项目采用低温多向轧制应力诱导技术制备原位自生纳米准晶增强的Mg-Zn-Er合金，综合考虑应力、温度和成分等因素，利用HRTEM、HAADF-STEM等技术研究纳米准晶形核/长大动力学特征，揭示纳米准晶的形成机制，结合TEM原位观察高温拉伸中纳米准晶与基体、位错、界面的交互作用，揭示纳米准晶对合金超塑性变形的影响规律，重点从微/纳角度阐明纳米准晶对裂纹、空洞的影响规律，揭示合金的超塑性变形失效机制，为基于利用热稳定钉扎粒子增强的高应变速率下可超塑性成形的镁合金材料设计提供科学依据。

本课题经过为期3年的研究，开发了超塑性优异的Mg-Zn-Er合金，取得了一定的科学结论，为后续中强高塑性Mg-Zn-Er合金开发奠定了坚实的理论和实践基础。本课题确定了有效的合金范围，获得了Mg-Zn-Er合金的热处理工艺；构建了Mg-Zn-Er合金的本构方程和热加工图，揭示了压缩变形中合金的塑性变形机制及动态再结晶机理；确立了Mg-Zn-Er合金板材的交叉轧制工艺，获得了一种胀形性能良好的镁合金板材；揭示了纳米准晶的形成规律及其调控原理，开发了一种超塑性性能优异的Mg-Zn-Er合金材料，其在300oC条件下拉伸，延伸率可达1000%以上；发表论文11篇、投递论文1篇，其中已发表/接收SCI论文8篇，发表EI论文2篇，授权中国发明专利3件。