块体纳米晶镁合金的微观组织、力学性能及其机理研究

本项目提出在氢化脱氢法制备晶粒尺寸约10nm的微纳二元结构镁合金粉末的专利技术基础上，利用放电等离子快速烧结技术，通过建立纳米晶镁合金等离子活化烧结过程的主烧结曲线，研究等离子活化烧结过程中纳米晶镁合金粉末的致密化与晶粒长大机制，获得10 -1000纳米之间的不同晶粒尺寸和多尺度混合晶粒的纳米晶镁及镁合金块体材料。对不同微观组织的纳米晶镁合金块体材料进行拉伸/压缩试验，分析并表征力学性能、应变硬化率等及其随应变速率的变化规律。同时研究并表征拉伸/压缩过程中晶体缺陷如位错、孪晶、晶界等的产生、演化与交互作用，及其对纳米晶镁合金应变硬化规律的影响，阐明纳米晶镁合金组织结构和力学性能之间的定量关系；探讨纳米尺度下镁合金的强韧化机制，建立纳米晶镁合金界面强韧化理论。为开发高性能镁合金材料提供理论基础及实验数据。

In this project, bulk nanocrystalline Mg and Mg alloys will be achieved by using spark plasma sintering (SPS) based on our patent technology of preparing nanocrystalline Mg and Mg alloys powders with micro-nano binary structure. The influence of various SPS parameters on the densification and grain growth of the nanocrystalline Mg and Mg alloys powder will be investigated by founding the master sintering curve. In order to study the relationship among the mechanical properties, the strain hardening rate and the strain rate the tensile and compression testing will be applied to the bulk nanocrystalline Mg and Mg alloys with grain sizes from 10 nm to 1000nm. Moreover, not only the generation, evolution and interaction of crystalline defects such as dislocations, twins and grain boundaries, et al, during the course of tensile/ compression testing, but also the effect of the above defects on the strain hardening principle of bulk nanocrystalline Mg and Mg alloys will be investigated, so as to illuminate the quantitative relation between the microstructure and mechanical properties of bulk nanocrystalline Mg and Mg alloys. As a result, the toughening mechanism and surface toughening theorem of bulk nanocrystalline Mg and Mg alloys will be discussed. Based on the above investigations, we plan to explore a new and effective technique to prepare Mg alloys with high performances.